Not to be annoying, just trying to add another data point... I do
no DDNS,
no OpenVPN, really just a vanilla system.
But my IPv6 - which has been working perfectly with my Comcast connection for the last 2+ years - is completely
gone after installing 386.4 BETA1 from the previous 386.3_2 release.
This is both immediately after the update and then after a forced reboot...
Put another way,
https://test-ipv6.com/index.html.en_US has given me "10/10" since the day I hooked up my RT-AX88U - but now, the exact same (untouched) "Native" and the rest of the defaulted settings result in the test site reporting "0/10", and no IPv6 addresses or components are shown on the device's IPv6 page.
So, I tried to read the posts in this "BETA1" thread that mentioned IPv6, and they seem to all (?) mention DDNS or OpenVPN - but since I have neither of those in use, there could be something more fundamental with the new code and IPv6 going on?
EDIT: So, I recalled that in the spring of 2019 (and then it became superflouous that summer), we got to add a "wan-start" script to /jffs/scripts, which did the following to enable IPv6:
echo "1" > /proc/sys/net/ipv6/conf/all/accept_ra
echo "1" > /proc/sys/net/ipv6/conf/all/forwarding
echo "1" > /proc/sys/net/ipv6/conf/eth0/accept_ra
echo "0" > /proc/sys/net/ipv6/conf/eth0/forwarding
... and then make it executable, reboot, etc.
Perhaps needless to say (but I thought I should add this in the spirit of "data point"), this appears to have no effect on the current dearth of IPv6.