I am not a scala fan and do not care for it, but I upvote for the thorough thought process, breakdown, and debugging of the problem. This is how technical blogs should be written. AI aint got shit on this.
It also looks like it has some improvements for dealing with `null` from Java code. (When I last used it I rarely had to deal with null (mostly dealt with Nil, None, Nothing, and Unit) but I guess NPEs are still possible and the new system can help catch them.)
If you're going to "refresh" a codebase you probably want it to be on the current version of things. Old dependencies rot, like it or not. I don't think there's any timeframe for Scala 2 EOL yet, but new development is happening in 3.
Why not though the upgrade process from 2.13 to 3 is pretty smooth. And you get all the new language features. I can think of a few that I actually like. I’ll just mention enums because it’s a good example.