Change 883558 had a related patch set uploaded (by Nikerabbit; author: Nikerabbit):

[translatewiki@master] Install DiscussionTools

https://gerrit.wikimedia.org/r/883558

Change 883558 merged by jenkins-bot:

[translatewiki@master] Install DiscussionTools

https://gerrit.wikimedia.org/r/883558

Discussion Tools is now available, but LiquidThreads is still shown by default. There doesn't seem to be any easy way than manually updating all existing talk pages to LiquidThreads. Once that is done, we can switch LiquidThreads off by default.

I am expecting this migration to never complete unless we find methods to automate this process for all remaining pages. https://translatewiki.net/wiki/Category:Discussion_pages_migrated_away_from_LiquidThreads can be used to track the migration process.

The scope of this task has been achieved, though, so I am marking this as done and closing if no issues are found in the next few days.

Flow has maintenance scripts for migrating from LQT to Flow and from Flow to wikitext.<ducks>

I have a vague memory that long time ago I tried the scripts and they were throwing PHP errors with our content.