I don't know honestly. With PHP 7.4.33 and the unfixed nl2br plugin I only see the "php-8.1-strftime.php" problem in the php.log. So maybe it does not need to be fixed with 7.4.33, yet?
Right, if you were under PHP 7.4 the bug would not have happened. The code was compatible with it. But the fix will help under PHP 8.
Btw, great to see that Serendipity 2.5.0 still really worked with PHP 7.4! :)
For php-intl, exactly. That's for the server hoster to activate. I'm surprised it isn't activated by default, it was already there on the hosters I'm using (uberspace, manitu).
That new requirement slipped under the radar, but even after noticing it I think we assumed it would basically be always enabled. Otherwise we should have written about the new requirement more often.