If temporary mails are blocked I usually try create a Protonmail account. If they want a phone number, I just reset Tor identity and try again, until they give me an option to verify with an email instead, then I just try a few temporary emails until one works. Lately it's taken me only one retry at most to get through.
In the past I also used Yandex since it was really easy to register while most websites consider it a legitimate provider. However their own captchas don't work over Tor anymore.
A much bigger problem than creating and using throwaway emails is that lots of websites effectively block Tor via infinite Google captchas on their registration and/or login forms.