You can transfer your Google Voice account to a regular GMail account despite their documentation claiming otherwise. See:
Keep in mind you can port out a Google Voice number, also if you pay for Apple services domain hosting is free for iCloud+ users now, although you don’t get as many addresses.
It is very frustrating. I did a lot with Google Apps on that domain, and migrating that stuff out to a consumer account is a painful process.
I'll lose important things like my Google Voice number that I've had for a decade unless I pay for a business account.