Just looking at emails: your choices are to trust someone else's domain -- likely gmail -- or own your own domain + some kind of forwarding or 3rd party mail service.
For gmail, you risk account lockout like OP is experiencing. You can mitigate the risk with more recovery options at account.google.com like backup codes.
For a service other than gmail, I think the risks of lockout without customer service to help might possibly be less., especially if its paid like fastmail. If you do pay you have the risk of not wanting to pay anymore, or forgetting to pay, and if you don't pay you also have the risk of the service going away. I suppose the service going away is ok.
I for one am pretty confident google will keep gmail running as well as possible, so I see other services as a bit more risk there.
If you own the domain, you have paid for it and risk someone stealing it or grabbing it when you forget to pay. You can mitigate the risk by choosing a registrar with good security, paying for a longer term or not forgetting, eg a quarterly reminder to review your domain names. You also need to be able to access your registrar account. You can choose registrars you get other services from, like AWS Route 53 if you use amazon for anything, or Cloudflare for VPN, and mitigate the risk of non-payment or non-access because access and payment will be done more frequently.
Using your own domain is also more moving parts, decisions, setup, etc. So you risk more things going wrong or fatigue over all the maintenance taking over. How you weigh the monetary and complexity cost of using a domain name for email compared to the upside of control, having a personal site at your own name, etc.
For gmail, you risk account lockout like OP is experiencing. You can mitigate the risk with more recovery options at account.google.com like backup codes.
For a service other than gmail, I think the risks of lockout without customer service to help might possibly be less., especially if its paid like fastmail. If you do pay you have the risk of not wanting to pay anymore, or forgetting to pay, and if you don't pay you also have the risk of the service going away. I suppose the service going away is ok.
I for one am pretty confident google will keep gmail running as well as possible, so I see other services as a bit more risk there.
If you own the domain, you have paid for it and risk someone stealing it or grabbing it when you forget to pay. You can mitigate the risk by choosing a registrar with good security, paying for a longer term or not forgetting, eg a quarterly reminder to review your domain names. You also need to be able to access your registrar account. You can choose registrars you get other services from, like AWS Route 53 if you use amazon for anything, or Cloudflare for VPN, and mitigate the risk of non-payment or non-access because access and payment will be done more frequently.
Using your own domain is also more moving parts, decisions, setup, etc. So you risk more things going wrong or fatigue over all the maintenance taking over. How you weigh the monetary and complexity cost of using a domain name for email compared to the upside of control, having a personal site at your own name, etc.