I have considered this, but converting is not risk free. Say I utilize my own domain backed by Gmail. I have increased my surface area by being reliant upon both Google and the security of my domain registrar. Perl.com was just stolen[0] due to some shenanigans -how I would I keep myself immune?
My fear with using my own domain is that if it is compromised, then an attacker can access all of my email linked accounts (eg banking). If Google shuts me down, at least I know the domain is secure and the email is dead and unable to be intercepted.
Banks use 2FA so stealing your email won't steal your account.
Anyway, you can appeal to the registrar and IANA for help if your registration is attacked.
I also do regular Google Takeout backups so that I at least have access to the majority of emails and google data.
I've yet to find a good solution for this without paying for Google's business product, which I find way too dangerous to risk. You can't get a custom domain on consumer gmail.
Anyway why is Google's paid business product more risky than their free Gmail?
1. You need to pay for a mail server, and then you lose the benefits of gmail's spam filters, and also you start having deliverability problems.
2. You lose the benefits of some of gmail's features as they don't classify forwarded emails the same.
Because as a person I have some rights under GDPR, as a business I don't really. Business accounts are even easier for them to shut, and using a business account for personal things sets off loads of red flags. You can't review products, you can use family features, your google home products get messed up, etc.
Just curious, why would you accept this risk? Even though the probability of losing your account is small, the impact is huge. I'd recommend at least backups and your own domain for an E-mail address (even if you just have Gmail continue to host the email).