While we aren't ready to commit to a release date just yet, the game has progressed far enough that we will be opening up playtesting to the public on a limited basis. Signups are currently open and will be taken on a randomized basis, hopefully as soon as this week.
The playtest will provide a mostly feature complete version of the game, but there are still a handful of features missing. Notably, achievement progress cannot be directly shared with the main release, though cloud data will be. There are also a handful of visual and audio issues that need addressing. Please report any issues you have to Steam Discussions or to the support email.
The initial release of the playtest will support Windows and OSX directly. Steam Deck has not received enough testing to know for sure one way or the other just yet, but initial trials from internal testing are promising. A native Linux build is planned for a future update.