Can I keep underlying Google accounts if I move the custom domain elsewhere?

[jedwood]

I know it's possible to sign up for a basic Google account (e.g. use Google Drive) with a custom domain that is not a Google-hosted domain. For example, I can create a functioning me@something.com Google account. My question is: can I convert existing accounts (Legacy GAFYD) with a custom domains into those basic non-Workspace accounts? Mostly looking to keep all the Docs/Sheets/Slides/Drive stuff in place, but use non-Gmail email.