Multi-player does not work in Stadia; clicking Multiplayer briefly shows the lobby screen before freezing and then crashing to a Stadia error that the game has glitched. Had this occur in Chrome browser (Version 85.0.4183.121 Official Build 64-bit) and on mobile (Pixel 3).
When starting the game you are not prompted to create a Larian account as is required in other platforms. I went to Larian.com, created an account, and linked my Stadia account to Larian. Signed out of Stadia, signed back in, verified Larian listed as a 3rd-party with access. No change, still cannot enter multiplayer
Potentially related, the Profiles selection in the main menu does not do anything. On other platforms, you must create a profile to click Multiplayer. I am neither prompted to do so, nor can manual click Profiles in order to make one.