As many of you are aware, ShoutWiki is planning to upgrade to MediaWiki 1.35, which, at the time of writing, is the current LTS version. However, I've noticed that MediaWiki 1.39, the next LTS version, is set to release in November, less than a month from now. Here is a all changes introduced in release candidate 1. It might be best to wait, to upgrade to 1.39 when it comes out instead of upgrading to 1.35 now.
Closing this as a WONTFIX as this task seems to be more aimed at skipping 1.35.
We're well aware of the progress on 1.39, after all, we both worked on upstream MediaWiki projects before we got involved with ShoutWiki, and that hasn't changed - we're also well acquainted with a number of WMF/upstream developers.
We're not going to skip 1.35 as we're very almost there with it, and is still expected to receive support for the next year. Additionally, there'd still be a lot of code to update and you wouldn't see 1.39 for a while.
If everything we've done in the last... however many years... has been successful, we should be able to roll out 1.39 a lot easier than previous updates. Well, that's the hope. Time will tell.