I know I saw this elsewhere but the primary delay seems to be the Slackware dependency. Slackware finally revised to 15 and RC2 looking at /etc/os-release was using a Slackware 15 RC. Slackware 15 didn't get officially released until the beginning of Feb 2022. Slackware is still pushing updates like they are going out of style as well. That said, Slackware is known to prioritize stability and they hadn't done a major point release since 2016 (14.2) and 2012 is when 14 came out so it was a major upgrade from a dependency perspective.
I imagine a full regression and any development for Unraid's work on top of that simply takes time. I'm equally frustrated since have had RC2 and there have been various KPs popping up from time-to-time. Unraid has announced a copy of times they are getting close so I imagine they are. That said, risking data isn't my idea of a good time although the hypocrite in me is running a RC so not sure what that says.
Anyways, I have no inside knowledge but wanted to share what is buried elsewhere in the forums, etc.