This page says "Warning: MediaWiki is not compatible with PHP 7.4.0 to 7.4.2 due to an upstream bug. See phab:T246594 for more information." Could we replace "bug" by plainer language? The phab page did not seem to be informative. This seems clearer, if it is correct:
"Warning: MediaWiki cannot run on PHP 7.4.0 to 7.4.2 because of a bug in PHP. See phab:T246594 for more information."