I am a PS4 player wondering if I can put runs on Java due to bedrock being pretty dead just out of curiosity

No. Bedrock Edition runs go on the Bedrock Edition board.

also these sort of questions should be posted to the Minecraft game forums and not the site forums

I'm sorry but, what kind of logic is that? How could you possibly justify putting a run of a particular game on a leaderboard for anything but that game?