You'll need to own Minecraft on the Play Store to be able to play on Linux, so that's one thing to keep in mind, also you'll need a Microsoft account to play online. There's not much else, the bedrock launcher is pretty good, and mostly keeps up with breaking changes to the android version.

As for why there are multiple Minecraft versions, blame Microsoft. When they bought Mojang they wanted a Minecraft version that worked on consoles and had better performance on lowered powered devices like phones, so they wrote a clone of the game in C++. And props to them, they got what they wanted, but the game isn't the same as the older Java game, so the core PC community never adopted Bedrock.

Edit: to be clear, the C++ codebase existed before the Microsoft purchase, but Microsoft was the one that pushed the unified Bedrock edition brand and expansion, and never bothered with Java compatibility.