I use Avast Browser on Windows 7, but it gives me an error in Gmail saying that it is not a suitable browser.

Avast Secure Browser
1

I use Avast Browser on Windows 7, but it gives me an error in Gmail saying that it is not a suitable browser.

2

IIRC latest Avast Secure Browser does not run on Windows 7 because of upstream (Chromium) restriction. Gmail might warn you about that.