I’m a backer but I have not recieved an invite to the android beta. This may have to do with my email being unsubscribed from some kickstarter stuff.
I’m in the same boat too.
It was in the notifications on the backer website. There is a link to google play.
Where is said backer website? Haven’t seen any such link, though Abe contacted me for my google account details.
I got involved through kickstarter and that is where my invite was.
Instructions for getting beta access on Android are here: https://www.kickstarter.com/projects/175814937/filmlab-an-app-for-viewing-and-digitizing-analog-f/posts/1959279
If the Play Store doesn’t let you opt in to beta access, it means the email address I have on file for you doesn’t match the one you’re using to log into the Play Store. If that’s the case, contact me with your Google account email address, and I’ll get it fixed