Steps to replicate the issue (include links if applicable):

• Turn off DiscussionTools at https://meta.wikimedia.org/wiki/Special:Preferences
• Visit https://meta.wikimedia.org/wiki/Meta:Babel on desktop
  • From the console run (per Installation) mw.loader.load('https://commons.wikimedia.org/w/index.php?title=User:Jack_who_built_the_house/convenientDiscussions.js&action=raw&ctype=text/javascript');
  • Observe it activates
• Visit https://meta.m.wikimedia.org/wiki/Meta:Babel
  • Load convenientDiscussions.js
  • Observe it does not activate (as expected)
• Visit https://meta.wikimedia.org/wiki/Meta:Babel on mobile (or use useformat=mobile)
  • Load convenientDiscussions.js
  • Observe it activates (not expected)

Other information (browser name/version, screenshots, etc.):

See also https://www.mediawiki.org/wiki/Requests_for_comment/Mobile_domain_sunsetting/2025_Announcement

I was able to find this proactively via the Global Search tool, thanks to the older non-obfuscated copy at https://www.mediawiki.org/wiki/User:Jack_who_built_the_house/convenientDiscussions.js:

if (!location.host.endsWith(".m.wikipedia.org")

The latest release is at https://commons.wikimedia.org/wiki/User:Jack_who_built_the_house/convenientDiscussions.js, but I would not have found that.

It looks like the latest source still has similar code:
https://github.com/jwbth/convenient-discussions/blob/v7.6.13/src/app.js#L305

if (
  /(^|\.)m\./.test(location.hostname) ||
  mw.config.get('wgPageContentModel') !== 'wikitext' ||
  mw.config.get('wgIsMainPage')
) {
  return;
}