For T266583: MediaWiki 1.35 should be compatible with PHP 8 per PHP support policy, we'll no doubt need to bump various libraries, both Upstream and Wikimedia maintained to include PHP 8.0 support
At a quick glance, current constraints that explicty mean they won't work (or even install!) on PHP 8.0
semver "php": "^5.3.2 || ^7.0"wikipeg "php": "^7.2"hotp-php "php": "^5.3.3 || ^7.0"
Plus the core-only (dev-only) one:
dbal "php": "^7.2"
And then obviously the dependancy tree of stuff that depends on it...