java virtual machine launcher +minecraft

Yes, Minecraft 1.12.2 can run well on Ubuntu 20.04, but it does require Java 8, usually listed as '1.8'. The docs at Minecraft Tutorials seems to indicate that 1.12 should run, so I'm hoping that's correct.

Is this different from the OpenJDK that I see, on the command line? Is that what the 'launcher update does'? And if so, how would I see what version of internal-Java is currently running? This question, Preferred Version?, seems to indicate there is a bundled version of Java with the installation. The Launcher screen does indicate that there's a 'new version of the launcher', but the notes give no indication of what it does or what version it is. After posting this, I found out that 1.16 added in a version of Customizing Worlds, but it's definitely different from 1.12. Basically, I wanted to experiment with the Custom Worlds options, which is in version 1.12 - but was removed from 1.13. Minor update on why I want to do this (and possibly other people might want to).

And if so, how? Or what versions of Java/launcher, do I need?

Java virtual machine launcher +minecraft