I'm currently using Migadu. It's $20/year for their cheapest plan. They give you a lot of control over the email service, so it might not be the best if you're a noob. In fact, they require you bring a domain name. But, they let you create unlimited users, aliases, have fancy routing, etc.

https://purelymail.com/ looks interesting too. And is cheaper at $10/year.

If you do decide to get a custom domain, just some tips:

• get something that ends in .net or even better .com because shitty companies with shitty IT departments will block other TLDs (I've had this happen with FedEx and my local garbage company). There is no spam folder for them, the email just explodes.
• probably don't pick a domain with one of your names it in for better anonymity, unless I guess you have a popular last name? john@smith.com looks cool, but consider if you want random sites like lemmy to have that data.
• don't pick a homophone or weird word because at some point you'll have to speak your email to another human and it's really awkward to tell your bank that your email is john@piggy.park or john@maill.com or was it john@male.com?

Also, the web interfaces of some of these other email services might not be as good as Gmail's UI. It helps to use an email client instead. Thunderbird is fine or you could use something simpler like claws-mail or even something like mutt.