Topic on Extension talk:UserMerge

False alert: someone flagged this extension as incompatible with 1.38, but either it was a small issue either it is solved since 3 July: it works with 1.38 and current master (1.39.0-alpha).

What happens if you install this extension on MediaWiki 1.38 or 1.39?

I'm not sure if it doesn't work - an anon IP added the original note about MW 1.38 incompatibility, and I don't see any open issues regarding it.

Should I consider this extension unmaintained?

It looks like it received updates as late as Jun 19th, and it's in use by some prominent releases, such as BlueSpice. I'm not sure if there's an official active maintainer.

I think you should just try it on a later version.

I and Kghbln reverted the warning given I just tested with MW 1.38 and 1.39 and it works. Perhaps phabricator:T281821 was an issue a few months ago, but it is solved.

If you have specific issues with the extension, please open a task on Phabricator and describe the issue. Be sure you use the lastest version of the extension in the branch REL1_38 (Git method), or you recently downloaded the latest version (branch 1.38) of the extension on Special:ExtensionDistributor/UserMerge.