Google finally allowed personal legacy free GSuite accounts to opt-out of “upgrade” to Google Workspace. You can continue using your custom domain with Gmail, retain access to no-cost Google services such as Google Drive and Google Meet, and keep your purchases and data.

The option is a little hidden in the admin console, but should be available in the following link:

https://admin.google.com/?action_id=SE_SELF_TRANSITION&utm_source=helpcenter

Note that it applies only for personal use, businesses will have to switch to one of the paid Google Workspace plans.

For me, it's too late. I already switched Mail, Calendar, and Contacts to another provider, but I'll at least be able to keep using Drive/Docs and keep mu Android purchases.