Looker studio REGEXP issue

I’m also using regex to differentiate hostnames (WHEN (REGEXP_MATCH(Page URL, ‘.www\.hostnameA.’)) THEN ‘Hostname A’). When I add this regex as a filter to a standard dashboard, f.e. comparing Channels & Visitors for one hostname in particular, I get somewhat weird results like the screenshot below.

Does regex works differently in looker studio than in the Piwik interface? Or will this issue have something to do with the matter Filters do not work with Data Studio Connector (from 28.11.) - #3 by dave
Screenshot 2023-02-14 at 15.20.35

Yes, Regexp matches are using full match instead of partial match. We have it on an improvement list, but in the meantime you can adjust your regexp to match full string you are filtering for.

You can check similar thread here: Looker Studio Connector: Regexp Matches don't work - #8 by loldenburg