While experimenting with gerrit #26302 that captures the logs, I noticed an error in TuleapSidebar:
2022-07-05 15:19:18 web plugin_mediawiki_102: [f0ee8c50fb310e22f3bf52e6] /mediawiki/gpig ErrorException from line 44 of /usr/share/mediawiki-tuleap-flavor/skins/TuleapSkin/src/TuleapSidebar.php: PHP Notice: Trying to access array offset on value of type null #0 /usr/share/mediawiki-tuleap-flavor/skins/TuleapSkin/src/TuleapSidebar.php(44): MWExceptionHandler::handleError()
#1 /usr/share/mediawiki-tuleap-flavor/skins/TuleapSkin/src/SkinTuleapSkin.php(163): TuleapSkin\TuleapSidebar->getConfiguration()
#2 /usr/share/mediawiki-tuleap-flavor/skins/TuleapSkin/src/SkinTuleapSkin.php(99): TuleapSkin\SkinTuleapSkin->makeTuleapProjectSidebarConfig()
#3 /usr/share/mediawiki-tuleap-flavor/includes/skins/SkinMustache.php(57): TuleapSkin\SkinTuleapSkin->getTemplateData()
#4 /usr/share/mediawiki-tuleap-flavor/includes/skins/SkinTemplate.php(144): SkinMustache->generateHTML()
#5 /usr/share/mediawiki-tuleap-flavor/includes/OutputPage.php(2622): SkinTemplate->outputPage()
#6 /usr/share/mediawiki-tuleap-flavor/includes/MediaWiki.php(954): OutputPage->output()
#7 /usr/share/mediawiki-tuleap-flavor/includes/MediaWiki.php(967): MediaWiki->{closure}()
#8 /usr/share/mediawiki-tuleap-flavor/includes/MediaWiki.php(547): MediaWiki->main()
#9 /usr/share/mediawiki-tuleap-flavor/index.php(53): MediaWiki->run()
#10 /usr/share/mediawiki-tuleap-flavor/index.php(46): wfIndexMain()
#11 {main}