Valve has begun the process of sending out invites for the Artifact 2.0 Beta Test. Here's the email we received, a video, and an opt-in link that should only work if you have previously purchased the game prior to March 30, 2020.

Quote From Valve

We are excited to announce the kickoff of Artifact Beta 2.0! We’ve decided to approach things a bit differently this time around by gradually inviting people to join us while we are still “Under Construction”.
The gameplay has progressed enough that we’d like to start testing with a wider group: We’ve streamlined the game, removed the old monetization, and added many Quality of Life features.
As we begin to invite people to join us, here are some works-in-progress you’ll notice:
· Placeholder art and temporary effects in places
· Changing cards, art, and even game rules as we go
· Play modes that are currently disabled for testing will gradually be enabled as we add more players
· Card collections and stats may be reset during the Beta
· We’re still working on the ability to do observed playtests during this time, so expect some usability issues as we work out those kinks

You can see some of the changes here:
(contains footage from a development build, some gameplay details have changed)

Click here to opt-in to the Beta.

The link above will only work for players with the original game on their Steam Account (it doesn’t need to be installed). We will use a lottery system to invite people who have opted in. Invites will start out slow, so don’t be discouraged if you don’t get in right away. We will give everyone a chance before switching to an Open Beta.

See you in the game!