Realized I should probably post this at the top level:

One of the biggest issues that I’ve had with the unofficial Bedrock launcher is that it limits render distance to the maximum that is available on mobile which is significantly less that the Steamdeck can handle. That said, the tradeoff is excellent battery life.

You could run a server which both Java and Bedrock players can join: https://geysermc.org/

But you might want to watch some tutorials if you’ve never set up a Minecraft server before.

There's an unofficial Bedrock launcher in Discover, it usually works for me! That being said I've had better luck running Java with a controller mod like Controllable. I run Geyser on my server so both clients work!

Thanks for all the feedback!

The flatpak (I think that's what people are talking about here) was what I was using before and IIRC, there was at least one point where the dev threw his hands up and stopped working on it, as someone (MS? Mojang? Google?) was making his life harder. That's probably my biggest complaint about Bedrock, actually. It's not nearly as buggy as its reputation claims, but lordy there's a lot of hands in that pot. And that's before you even start talking about cross play from the Switch...

I was actually hoping to hear that somehow Proton and the Windows version of Bedrock was the way to go these days, but glad that there's at least something.

I 've been playing minecraft bedrock using the steam deck, over LAN with my daughter on the Windows PC. We needed two Minecraft accounts $29 from Microsoft. The deck controls worked identical to Xbox controller once I loaded the Minecraft bedrock launcher from the discover app and added it as a non steam game to game mode. That was the key to get the controller to behave right. It all works like a dream now and is super fun!