I upgraded my main firewall/router to Leap 15.1, and since then several things
about IPv6 do not work anymore:

- the external interface does not accept RA anymore even though
net.ipv6.conf.all.accept_ra = 1 and net.ipv6.conf.eth1.accept_ra = 2 are set
properly, like they have been set in 15.0
- the firewall does not forward IPv6 traffic anymore

Fun part: The part about not accepting RA information anymore only started a
few reboots after the upgrade; before that I could still talk IPv6 from the
firewall itself, but obviously not from any machine behind it.