How to sign in Google Messages on computer via QR Pairing in 2026 [Solved]

First, I know Google Messages is non-free software. But right now, it's the only app that can be used to send RCS messages from computer. So it might be useful for Trisquel community that doesn't want to make a Google account, like me.

As you may know, Google removed the option to sign in Google Messages with QR Pairing.
Now, they force you to do it ONLY with a Google account. People who don't have and don't want to create one, or people that just prefer QR pairing can still do it. But with a workaround:

1) Download (or use) a Google Messages version that still allows QR pairing (like one from January 2026). It can be downloaded from Uptodown store. I tried installing it from an apk directly but it failed.
2) Open the link: https://messages.google.com/web/authentication
3) Sign in following the instructions on the screen.

Do it as soon as possible because Google might remove this option soon.