could you provide a descriptive PHP error message? see https://www.mediawiki.org/wiki/Manual:How_to_debug#PHP_errors

Sure can do ;-)

Fatal error: Class 'MWLoggerFactory' not found in /var/www/wiki/extensions/CirrusSearch/includes/ElasticsearchIntermediary.php on line 175

I used the corresponding version of CirrusSearch
https://www.mediawiki.org/wiki/Special:ExtensionDistributor?extdist_name=CirrusSearch&extdist_version=REL1_25&extdist_submit=

So I now tried the "Master" version of CirrusSearch, and here we go. Now the "special page" "Version" is working again. The extension is still showing up as version 0.2 which could be updated, but at least it is working. Maybe someone can fix the 1.25 version of the download.

CirrusSearch is not correctly branched for REL1_25... I hope this is not T66157 strikes back again :(

For the meantime, you can try downloading the master version and see if it just works.

Yes, everything works with the "master" version. Thank you again fort CirrusSearch, one of the best improvements in the last couple of years on mediawiki!!!

Change 214094 had a related patch set uploaded (by BryanDavis):
Use namespaced \MediaWiki\Logger\LoggerFactory

https://gerrit.wikimedia.org/r/214094

Change 214094 merged by jenkins-bot:
Use namespaced \MediaWiki\Logger\LoggerFactory

https://gerrit.wikimedia.org/r/214094

Yes, now if you download the corresponding version for MediaWiki 1.25 the download is ok and the files work. Great job, thank you!