UPDATE: The first 3 times I visited the site, all I got was a bunch of log in options that didn't look like the "log in with the Alby browser extension" button that I needed.
I was about to give up but I decided to try clicking the site URL one more time. That time, the site apparently noticed my browser extension and gave me a "log in with Alby browser extension" button.
Not sure what the hell happened but I probably couldn't log in again if I tried.