Use your own domain to sign up for a paid email service, provided by a company that focuses on email. I use Fastmail, but there are many other options.

Set up forwarding in Gmail to your new address.

Then, whenever you log in to a website or app with your Gmail, take a moment to change it to your new address. In a few weeks, most of your important accounts will be covered. In a few months, almost everything you still actively use will be done.

I did this ~5 years ago and the only thing that still arrives at my Gmail is spam.

Register your own domain, use a third-party provider to handle actual sending and receiving (I use proton, which makes the setup very easy), forward your Gmail to your personal domain address and as renewals and reminders come in switch your email on services to your personal domain.

After a year or two losing Gmail becomes an inconvenience; after a few more years it is nothing. As everything is now on your own domain name you can switch providers without affecting anything.

That's what I did about 5 years ago and my only regret is not doing it earlier.

I just sold a domain I had for 25 years and used for everything including API endpoints, email, authentication, etc. It took a couple weeks to transition myself and my family/friends.

Pretty sure just moving emails would have take a lot less effort. I had the advantage of keeping the domain until I was ready to move, now imagine Google just turned it off one day and what your workload would be. I shudder to think about having to deal with that.

I switched to my own domain ages ago; it only took 2-3 years to stop getting relevant mail to the old one (I put a forwarding rule in place and just used the new one for everything).

Imported all my past mail on day one, forwarding meant I had one inbox only, and I only sent mail from the new domain. A few gentle “please stop using my old address” conversations with family.

I moved away from a gmail address that was that old, dating back to the invitation-only days. It had become more spam than not, mostly other people who share my initials not knowing their own email addresses. But the possible devastation you mention was more worrying. It had become too much of a risk for my banking and identity generally to not own my email address.

I got a custom domain. I still host it on google, because I know how impossible it is for small companies to have a reasonable program to deal with insider threats. Because of that, I think only one of the giant companies can realistically provide secure email. And the google app suite is great. Now that I pay for google workspace, there's support and appeals available, and if they ban me anyway, I still control the domain and can regain access to everything.

I have not been able to delete the old address, even after 3 years. There are some things like Google Fi that can only use a non-workplace google account. Very, very rarely, I still get an email that matters on it. But I got to the point where I could stop checking it in about 2 months, and now I look at it about once a week quickly, more out of habit than anything else.

The switch was annoying, but not "hard". It was worth it.

Just start changing addresses. Forward the rest. It takes about a year. Changing your name is way harder and tons of folks do that all the time.

gmail uses IMAP.

make another mailbox (another provider - migadu, fastmail, proton, whoever) that has IMAP as well. (selfhosting.. is PITA. only if u really need it).

install some standalone mail-client - thunderbird, clawsmail, applemail, or k9 , aqua on android, whatever. Attach both mailboxes into that. Find out how to copy an e-mail from one folder into another.

Folder by folder, select all mails, copy from one mailbox into the other. Will take time.

(Beware, some clients (apple) will fuckup the mail-date, anything older than 5 years becomes 5 years old. or it shows like that. YMMV.)

i have made this multiple times, for 20+ years of mails...

Get your own domain so you can easily change providers in the future. Start with your password manager and change the address on all the accounts you have in there.

After a few years you'll notice you stop bothering to check your Gmail and you can delete it to close the address.

If you need motivation, skim the /r/GMail subreddit and see how many people are getting locked out daily.

It will never be easier than right now. Every day you stay, you dig their moat around you even deeper

I just went through all accounts in my password manager, logged in and changed my email. It takes a little while but not that much.

took about 30 minutes to switch to proton mail

Sign up at fastmail.com, set up forwarding, change your "reply-to" address. A year later, you'll have nothing arriving in gmail except marketing cruft.

Same. I still have an old Gmail address that receives forgotten but still considered important emails from various services.

What's the playbook for migrating away in this situation?

Just have to get started and suffer for a while and make it a practice to switch emails when you log into places.

I switched to fastmail with my own domain.