I used a legacy GSuite free account for many years until it just got too painful because of how Google actively prevents those accounts from using its ecosystem (can't use Nest, can't use Family Share or family YouTube plans, and the latest one: you can no longer add such users to Google Homes for voice match).

I moved email to MXRoute and spent some painful time migrating to standard Google accounts-- imapsync to copy some email over to the new account, hacking Partner Share to get photos moved over, resetting all the Home devices.

It worked great with a couple caveats. All my store purchases and $75 of credit are on the old account and they cannot be migrated. This means I keep my GSuite account as a secondary account on the phone, not a huge deal. I lost location history and other such unmigratable metadata.

I use K9 Mail and Thunderbird and am generally pleased with them. After a week of tweaking I see better spam handling than Gmail, which was a surprise.

Overall very glad I got it done.