Actually keeping your recovery options recent is the trick. Print out your recovery codes or store them somewhere safe. Check regularly (yearly, maybe more often) that there's a way to access your critical accounts.
For Google, you can also grab the cheapest Android phone you can find, sign in, and maybe boot it once a month or so to keep the tokens active.
If you've set up your account to only accept one source of 2FA and you lose thst source of 2FA, you lose your account. Same happens when you set up your account to only accept your password and then lose your password. If you lose your recovery email/2FA backup codes, you lose access, unless you're special enough to convince customer support that you are who you claim you are and not just a bot trying to hack you.
If you've lost your account and haven't set up any recovery mechanisms, you're probably out of luck. Your best bet will be looking for an old browser session with enough trust from Google's side to get access without reconfirming your 2FA trust.