If you tie yourself to a commercial platform, it’s gonna take advantage of you. That’s how they make money. So, I would also recommend using an open-source game engine like Godot and then distributing on multiple platforms.

The closest open-source thing to the Roblox model, that I can think of, is Luanti, which is basically a game engine and distribution platform for Minecraft-like games. Don’t expect to make money off of it, though.