August 6th, Tuesday. Eastern Timezone.
The PlayTest is planned to accommodate up to 500 players for its first batch. This is by no means a limit but a buffer to potential chaos. More players will be accepted if there is any in the weeks following, and until the PlayTesting is over.
PlayTest is planned to last until early access. Once you are in, you are in!
Though players say the game is quite stable, the game is still considered in heavy development as there are a number of features yet to be added to the game. As such, theres a lot of testing. Feedback and constructive criticism are the most valuable resource that one can provide during the PlayTest and the best places to do so, are in discord, and the steam community section.
The button for the PlayTest will not be visible, until the 6th.
To join the PlayTest, on the 6th you will need to go to the game's store page. And somewhere under the game's screenshots you will find a green button that mentions joining or requesting access to the PlayTest. After you request acess, unless it's full, which I don't think the limits will be reached. Then you should get access immediately and the game will show up in your game library for download.
If by chance it's full, you will simply be put in a wait list and will receive an email when you gain access.