[qwertox]

Is it really worth the hassle to move to another provider/self-hosted server for such a temporary problem?

Moving to another provider would mean to set up a new account, and usually the free tiers won't allow to use your own domain. So you would be locked to a new provider where you could face the same problems.

Temporarily moving to a self-hosted server would be an option, but probably just to receive emails during this time. You'd have to set up your certificate, and optionally DKIM, DMARC, SPF or whatever is required to ensure that your sent emails arrive properly. I can't imagine self-hosting email being something which won't give you a hard time every now and then.

Generally yes, I am in favor of owning your email-domain, but then using it with a professional provider like mailbox.org unless you really know enough about the topic.

But in this case, where the issue is a DDoS attack, I wouldn't do anything, since all undelivered email will be re-sent at a later time.