I mean, suit yourself if you insist that you can or only want to do it with a throwaway. I’m saying you can do it with similar services like tutanota as the failover address, eliminating the need for a throwaway.

You can simply use either: a different protonmail address or a similar service like tutanota.

Contact the DPA of your EU home country. It doesn’t matter of you live elsewhere.

Even non EU citizens can make complaints. It just won’t lead to remediation for their dircet issues, if one is sought through the DPA

It depends on where you live. But reddits EU offices are in the Netherlands, so you could file a complaint with them. Usually it should be as simple as searching for “gdpr supervisory agency [my state/country]” to find their website and complaint form.