I searched for other issues but somehow missed it! Apologies for the duplicate.

I am no longer able to launch versions before 1.17, such as 1.8.9 and 1.16.5, with Java 16.

I get a crash message saying my Java version is incompatible, despite being able to use Java 16 a few days ago.

I cant find a log file, it appears the game doesn't get that far.

I am however able to launch 1.8.9 in MultiMC, with Java 16.

I suspect it is to do with 1.17 updating to Java 16, however it only started recently, a few weeks after the release of 1.17.