There’s dhaaga which supports Mastodon and Bluesky, apparently.

NSFW warning, btw

From my understanding, Discord Search API is heavily rate-limited. If you have a lot lot of messages (say, removing ALL of your message history in ALL servers) then this would theoretically be faster.

Paid subscription of Proton bundles SimpleLogin, an email aliasing service. So you can have your personal email with your surname, and when you want to sign up to some shady corpo site, you give them a randomly generated email address using SimpleLogin. All emails sent to that alias email will be automatically forwarded to your personal email. You can then disable the alias email anytime and stop receiving emails.