I just updated the bundle to the lates version while using MW1.35.0. As soon as I wanted to mark a page for translation I got a fatal error message.
[YVOQeS7S@b1XulxvQpOXrwAAANU] /index.php?title=Spezial:%C3%9Cbersetzung_von_Seiten&target=Hauptseite&do=mark Error from line 40 of /www/htdocs/w014d7f1/wiki.designerthan.at/extensions/Translate/src/PageTranslation/TranslationUnitStoreFactory.php: Undefined constant 'DB_PRIMARY'
Backtrace:
#0 /www/htdocs/w014d7f1/wiki.designerthan.at/extensions/Translate/tag/TPParse.php(141): MediaWiki\Extension\Translate\PageTranslation\TranslationUnitStoreFactory->getWriter(Title)
#1 /www/htdocs/w014d7f1/wiki.designerthan.at/extensions/Translate/tag/TPParse.php(80): TPParse->loadFromDatabase()
#2 /www/htdocs/w014d7f1/wiki.designerthan.at/extensions/Translate/tag/SpecialPageTranslation.php(589): TPParse->getSectionsForSave(integer)
#3 /www/htdocs/w014d7f1/wiki.designerthan.at/extensions/Translate/tag/SpecialPageTranslation.php(240): SpecialPageTranslation->checkInput(TranslatablePage, boolean)
#4 /www/htdocs/w014d7f1/wiki.designerthan.at/extensions/Translate/tag/SpecialPageTranslation.php(98): SpecialPageTranslation->onActionMark(Title, integer)
#5 /www/htdocs/w014d7f1/wiki.designerthan.at/includes/specialpage/SpecialPage.php(600): SpecialPageTranslation->execute(NULL)
#6 /www/htdocs/w014d7f1/wiki.designerthan.at/includes/specialpage/SpecialPageFactory.php(635): SpecialPage->run(NULL)
#7 /www/htdocs/w014d7f1/wiki.designerthan.at/includes/MediaWiki.php(307): MediaWiki\SpecialPage\SpecialPageFactory->executePath(Title, RequestContext)
#8 /www/htdocs/w014d7f1/wiki.designerthan.at/includes/MediaWiki.php(940): MediaWiki->performRequest()
#9 /www/htdocs/w014d7f1/wiki.designerthan.at/includes/MediaWiki.php(543): MediaWiki->main()
#10 /www/htdocs/w014d7f1/wiki.designerthan.at/index.php(53): MediaWiki->run()
#11 /www/htdocs/w014d7f1/wiki.designerthan.at/index.php(46): wfIndexMain()
#12 {main}
By searching for Undefined constant DB_PRIMARY I found that this is the name that MW1.35.3 uses.
Maybe someone can add a notice somewhere on the page about that issue or just alter the compatible version.