If you want to try where I have got to so far, and I am not quite ready for a PR yet, but you can try it, you'll need to switch the dev stream. Once you have done that, then update. That will update the binaries as needed.
Jun 15 19:40:14 opnsense radvd[41741]: sendmsg: Permission denied
Jun 15 19:37:57 opnsense radvd[41609]: version 1.15 startedJun 15 19:37:57 opnsense radvd[41609]: no auto-selected prefix on interface igb1, disabling advertisementsJun 15 19:37:57 opnsense radvd[41609]: no auto-selected prefix on interface igb2, disabling advertisements
It's# opnsense-revert opnsenseor# opnsense-revert opnsense-develdepending on the installed release type.And it's# cd /usr/core# make upgradeCheers,Franco
Did you turn off assisted in RADVD and select managed before deciding it did not hand out leases? Mine did.