Hello,
I’m kind of seeing this.
My gateway has dhcpv4 and dhcpv6 as well as ipv6 router advertisements, and near enough every v6 capable device is happy.
I set my FP6 up yesterday and it initially was fine, has two privacy-prefix /64 addresses on my public subnet, two privacy prefix addresses on ULA and one link local address.
But after a while, ipv6 on wifi seems to stop working. I wrote a quick website a while back to test public addressing and the v4 works fine but v6 stops making connections. Wifi settings show that the connection still has all of the same addresses as before.
It has a material effect of making some apps requiring network access slow as they hang whilst the ipv6 connection fails before falling back to v4.
If I turn off wifi and back on after a few seconds, then retest, it all goes back to normal for a while.
My other android devices are fine; one using lineageos 22.2 (android 15) and another with android 13. Both have v6 which works without breaking down.