I was configuring 8.0b1 on my Pixel 6a with the September Android update. Over a dozen accounts. There was one that I could not change the Account Name (under General Settings) to a different string. Trying several different strings, all caps, all lowercase, mixed case etc did not hold when I went back to the previous settings menu list of my existing accounts. It was the 4th or 5th account name I had changed during that configuration session. If that matters. I did a swipe away close action, and restarted Thunderbird Beta, and the last name I had used showed up. From then on it worked, but I did not need to change any more. Maybe this will help someone else or the devs figure out what might have glitched during my configuration.