Sorry für’s aufwärmen, aber irgendwie suche ich mir den Wolf.
Gluon 2018.2, ffho-autoupdater-wifi-fallback. Es tut im Grunde, aber nur für v4, was bzgl. des Autoupdaters genau gar nicht hilft 
Thu Sep 10 22:24:05 2020 local0.info autoupdater-wifi-fallback: going to fallback mode
Thu Sep 10 22:24:05 2020 local0.info autoupdater-wifi-fallback: connectivity check failed
Thu Sep 10 22:24:05 2020 kern.info kernel: [325660.056992] IPv6: ADDRCONF(NETDEV_UP): tmp.mesh0: link is not ready
Thu Sep 10 22:24:07 2020 local0.info autoupdater-wifi-fallback: connect to radio0 KreisGT.freifunk.net 56:92:C9:3E:87:60
Thu Sep 10 22:24:07 2020 daemon.notice netifd: Interface 'mesh_radio0' is disabled
Thu Sep 10 22:24:07 2020 daemon.notice netifd: Interface 'mesh_radio0' has link connectivity loss
Thu Sep 10 22:24:07 2020 kern.info kernel: [325661.886811] device client0 left promiscuous mode
Thu Sep 10 22:24:07 2020 kern.info kernel: [325661.891966] br-client: port 4(client0) entered disabled state
Thu Sep 10 22:24:07 2020 kern.info kernel: [325662.287675] batman_adv: bat0: Interface deactivated: mesh0
Thu Sep 10 22:24:07 2020 kern.info kernel: [325662.293484] batman_adv: bat0: Removing interface: mesh0
Thu Sep 10 22:24:07 2020 daemon.notice netifd: Interface 'mesh_radio0' is now down
Thu Sep 10 22:24:08 2020 daemon.notice hostapd: client0: interface state ENABLED->DISABLED
Thu Sep 10 22:24:08 2020 daemon.notice hostapd: client0: AP-DISABLED
Thu Sep 10 22:24:08 2020 daemon.notice hostapd: client0: CTRL-EVENT-TERMINATING
Thu Sep 10 22:24:08 2020 daemon.notice hostapd: nl80211: deinit ifname=client0 disabled_11b_rates=0
Thu Sep 10 22:24:08 2020 daemon.notice hostapd: nl80211: Failed to remove interface client0 from bridge br-client: Invalid argument
Thu Sep 10 22:24:09 2020 user.notice mac80211: Failed command: iw phy phy0 set antenna all all
Thu Sep 10 22:24:09 2020 kern.info kernel: [325664.288566] IPv6: ADDRCONF(NETDEV_UP): fallback: link is not ready
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.490909] fallback: authenticate with 56:92:c9:3e:87:60
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.514553] fallback: send auth to 56:92:c9:3e:87:60 (try 1/3)
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.523681] fallback: authenticated
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.542801] fallback: associate with 56:92:c9:3e:87:60 (try 1/3)
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.556471] fallback: RX AssocResp from 56:92:c9:3e:87:60 (capab=0x421 status=0 aid=1)
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.565242] fallback: associated
Thu Sep 10 22:24:10 2020 kern.info kernel: [325664.569424] IPv6: ADDRCONF(NETDEV_CHANGE): fallback: link becomes ready
Thu Sep 10 22:24:10 2020 daemon.notice netifd: radio0 (16216): fallback (phy #0): unknown event 46
Thu Sep 10 22:24:10 2020 daemon.notice netifd: radio0 (16216): cat: can't open '/var/run/wpa_supplicant-fallback.pid': No such file or directory
Thu Sep 10 22:24:10 2020 daemon.notice netifd: radio0 (16216): WARNING (wireless_add_process): executable path /usr/sbin/wpa_supplicant does not match process path ()
Thu Sep 10 22:24:10 2020 daemon.notice netifd: radio0 (16216): Command failed: Invalid argument
Thu Sep 10 22:24:10 2020 daemon.notice netifd: Network device 'fallback' link is up
Thu Sep 10 22:24:10 2020 daemon.notice netifd: Interface 'fallback' is enabled
Thu Sep 10 22:24:10 2020 daemon.notice netifd: Interface 'fallback' has link connectivity
Thu Sep 10 22:24:10 2020 daemon.notice netifd: Interface 'fallback' is setting up now
Thu Sep 10 22:24:10 2020 daemon.notice netifd: fallback (16359): udhcpc: started, v1.28.4
Thu Sep 10 22:24:10 2020 daemon.notice netifd: fallback (16359): udhcpc: sending discover
Thu Sep 10 22:24:11 2020 daemon.notice netifd: fallback (16359): udhcpc: sending select for 10.255.6.192
Thu Sep 10 22:24:11 2020 daemon.notice netifd: fallback (16359): udhcpc: lease of 10.255.6.192 obtained, lease time 600
Thu Sep 10 22:24:11 2020 daemon.notice netifd: Interface 'fallback6' is enabled
Thu Sep 10 22:24:11 2020 daemon.notice netifd: Network alias 'fallback' link is up
Thu Sep 10 22:24:11 2020 daemon.notice netifd: Interface 'fallback6' has link connectivity
Thu Sep 10 22:24:11 2020 daemon.notice netifd: Interface 'fallback6' is setting up now
Thu Sep 10 22:24:11 2020 daemon.notice netifd: Interface 'fallback' is now up
Thu Sep 10 22:24:11 2020 daemon.info dnsmasq[708]: reading /tmp/resolv.conf.auto
Thu Sep 10 22:24:11 2020 daemon.info dnsmasq[708]: using local addresses only for domain lan
Thu Sep 10 22:24:11 2020 daemon.info dnsmasq[708]: using nameserver 10.255.0.61#53
Thu Sep 10 22:24:11 2020 daemon.info dnsmasq[708]: using nameserver 192.251.226.23#53
Thu Sep 10 22:24:11 2020 daemon.info dnsmasq[708]: using nameserver 1.1.1.1#53
Thu Sep 10 22:24:33 2020 local0.info autoupdater-wifi-fallback: execute the autoupdater
Thu Sep 10 22:29:11 2020 daemon.notice netifd: fallback (16359): udhcpc: sending renew to 10.255.0.61
Thu Sep 10 22:29:12 2020 daemon.notice netifd: fallback (16359): udhcpc: lease of 10.255.6.192 obtained, lease time 600
Thu Sep 10 22:29:33 2020 local0.info autoupdater-wifi-fallback: connect to radio0 KreisGT.freifunk.net 24:A4:3C:B2:11:D9
Thu Sep 10 22:29:34 2020 daemon.notice netifd: Interface 'fallback' has link connectivity loss
Thu Sep 10 22:29:34 2020 daemon.notice netifd: fallback (16359): udhcpc: received SIGTERM
Thu Sep 10 22:29:34 2020 daemon.notice netifd: Interface 'fallback' is now down
Thu Sep 10 22:29:34 2020 daemon.warn dnsmasq[708]: no servers found in /tmp/resolv.conf.auto, will retry
Thu Sep 10 22:29:34 2020 daemon.notice netifd: Interface 'fallback6' is now down
Thu Sep 10 22:29:34 2020 daemon.notice netifd: Interface 'fallback6' is disabled
Thu Sep 10 22:29:34 2020 daemon.notice netifd: Network alias '' link is down
Thu Sep 10 22:29:34 2020 daemon.notice netifd: Interface 'fallback6' has link connectivity loss
Thu Sep 10 22:29:34 2020 kern.info kernel: [325988.828654] fallback: deauthenticating from 56:92:c9:3e:87:60 by local choice (Reason: 3=DEAUTH_LEAVING)
Thu Sep 10 22:29:36 2020 user.notice mac80211: Failed command: iw phy phy0 set antenna all all
Thu Sep 10 22:29:36 2020 kern.info kernel: [325990.226683] IPv6: ADDRCONF(NETDEV_UP): fallback: link is not ready
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.498035] fallback: authenticate with 24:a4:3c:b2:11:d9
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.521558] fallback: send auth to 24:a4:3c:b2:11:d9 (try 1/3)
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.530691] fallback: authenticated
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.539114] fallback: associate with 24:a4:3c:b2:11:d9 (try 1/3)
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.550138] fallback: RX AssocResp from 24:a4:3c:b2:11:d9 (capab=0x21 status=0 aid=3)
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.558770] fallback: associated
Thu Sep 10 22:29:37 2020 kern.info kernel: [325991.566984] IPv6: ADDRCONF(NETDEV_CHANGE): fallback: link becomes ready
Thu Sep 10 22:29:37 2020 daemon.notice netifd: radio0 (16747): fallback (phy #0): unknown event 46
Thu Sep 10 22:29:37 2020 daemon.notice netifd: radio0 (16747): cat: can't open '/var/run/wpa_supplicant-fallback.pid': No such file or directory
Thu Sep 10 22:29:37 2020 daemon.notice netifd: radio0 (16747): WARNING (wireless_add_process): executable path /usr/sbin/wpa_supplicant does not match process path ()
Thu Sep 10 22:29:37 2020 daemon.notice netifd: radio0 (16747): Command failed: Invalid argument
Thu Sep 10 22:29:37 2020 daemon.notice netifd: Network device 'fallback' link is up
Thu Sep 10 22:29:37 2020 daemon.notice netifd: Interface 'fallback' has link connectivity
Thu Sep 10 22:29:37 2020 daemon.notice netifd: Interface 'fallback' is setting up now
Thu Sep 10 22:29:37 2020 daemon.notice netifd: fallback (16861): udhcpc: started, v1.28.4
Thu Sep 10 22:29:37 2020 daemon.notice netifd: fallback (16861): udhcpc: sending discover
Thu Sep 10 22:29:38 2020 daemon.notice netifd: fallback (16861): udhcpc: sending select for 10.255.6.192
Thu Sep 10 22:29:38 2020 daemon.notice netifd: fallback (16861): udhcpc: lease of 10.255.6.192 obtained, lease time 574
Thu Sep 10 22:29:38 2020 daemon.notice netifd: Interface 'fallback6' is enabled
Thu Sep 10 22:29:38 2020 daemon.notice netifd: Network alias 'fallback' link is up
Thu Sep 10 22:29:38 2020 daemon.notice netifd: Interface 'fallback6' has link connectivity
Thu Sep 10 22:29:38 2020 daemon.notice netifd: Interface 'fallback6' is setting up now
Thu Sep 10 22:29:38 2020 daemon.notice netifd: Interface 'fallback' is now up
Thu Sep 10 22:29:38 2020 daemon.info dnsmasq[708]: reading /tmp/resolv.conf.auto
Thu Sep 10 22:29:38 2020 daemon.info dnsmasq[708]: using local addresses only for domain lan
Thu Sep 10 22:29:38 2020 daemon.info dnsmasq[708]: using nameserver 10.255.0.61#53
Thu Sep 10 22:29:38 2020 daemon.info dnsmasq[708]: using nameserver 192.251.226.23#53
Thu Sep 10 22:29:38 2020 daemon.info dnsmasq[708]: using nameserver 1.1.1.1#53
Thu Sep 10 22:29:38 2020 daemon.err odhcp6c[16913]: Failed to send RS (Address not available)
Thu Sep 10 22:29:59 2020 local0.info autoupdater-wifi-fallback: execute the autoupdater
Wie gesagt, v4 tut, aber nix von v6 zu sehen:
root@33332-FWTest-a0f3c1058b90:~# ip addr show
[…]
1234: fallback: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
link/ether 5e:71:cf:f9:41:83 brd ff:ff:ff:ff:ff:ff
inet 10.255.6.192/20 brd 10.255.15.255 scope global fallback
valid_lft forever preferred_lft forever
inet6 fe80::5c71:cfff:fef9:4183/64 scope link
valid_lft forever preferred_lft forever
root@33332-FWTest-a0f3c1058b90:~# cat /proc/sys/net/ipv6/conf/fallback/accept_ra
2
Ich hab’ auch schon ebtables mal deaktiviert, hat auch nix geändert Any hint appreciated.