Minecraft 1.12.2 works really well on the RPi4! By allocating 512MB to GPU on the 2GB Pi, the game world generates much faster and tends to run between 20 and 30 fps. It plays really well now!
One thing to note with Raspbian OS Buster, it doesn’t have the correct jvm library, so I needed to copy “/usr/lib/jvm/jdk-8-oracle-arm32-vfp-hflt” from an older Pi image.
Btw should it be possible to run multiplayer between two Pis running this version of Minecraft? I couldn’t get it to work after opening the game to LAN.