Ok I've just updated to php8 :: Confirmed :: I'm getting lots of issues :)

Reverting to 7.4 for now
I am listing the errors/warnings I get and the changes I make
https://forums.b2evolution.net/updating-php-from-7-4-to-8

I'm also looking at the list of changes that maybe required via
https://www.php.net/manual/en/migration80.php

Good to hear that someone competent is looking at this! :-)
My PHP skills are far from what anyone could consider helpful, but I will be happy to help with testing, if needed.

Believe me competence is a matter of time and space and my main job is managing 40 acres of land without animals and powered machines to grow food etc, so time and space are very overloaded and unlikely to change in the next season.

The more skillz you have -- the less time you have... A known equation...

What are you growing? (Pardon the forum moderator part of you for the off-topic question.)