Actually Joomla 3 and Seblod run on PHP 8. If you have problems regarding this topic, check your custom templates. I just did an update to PHP 8 with a big multisite Joomla 3/Seblod site with lots of different content-types.
But yes, the problem you talking about ist really annoying. At the moment i'm thinking to move to wordpress with my Joomla3/Seblod sites because i dont want to start these updates 2 weeks before joomla 3 updates end.
The problem is, seblod is much smoother to work with in bigger projects, wordpress needs much more custom coding to achive same result.
Seblod team should give some infos to the community now. Personally i would upgrade to professional support with a finished version of Seblod 4, no problem. But leaving the community with total silence is not very friendly.
Maybe Octopoos could provide some infos what tasks still need to be solved and if there is anything, the community could do to help.