We are currently working hard on introducing controller support.
This is a large and complex task, so it has taken some time (and may take a little more). Once everything is ready, the version with controller support will be released in the beta branch.
The purpose of controller support, as I see it, is:
Specifically for players who enjoy playing with a controller, even on PC
More comprehensive support for Steam Deck
Subsequent porting to other platforms (of course, after the game exits early access)