In OpenWrt (Luci UI), Network -> Interfaces -> LAN -> "Accept router advertisements" (check this, reboot router). Under Network -> Interfaces the LAN interface should now list an IPv6 /64 in ...

The OpenWRT One router is designed to be unbrickable, with 'software freedom and right to repair' firmly in mind.

It's hard to choose between DD-WRT or OpenWrt for a custom router firmware. Which one has the best features and is the easiest to use?