I have received phishing attempts for cryptoscams that still had my tagged address and identified the source of the leak that way... but I'm sure there are more cautious scammers and spammers who removes it, still can be the poorman's version of a catchall address I guess.

Fastmail already provides this feature if you have a custom domain.

If you have 'domain.com' you can receive emails either on 'foo@domain.com' or 'bar@foo.domain.com' without problems.

It sounds like panix already did.

Fastmail lets you make as many redirects as you want, no + in them.

You can even get an api key for it and plug that into bitwarden, so that when you sign up for whatever, you click bitwarden, generate password, generate email, sign in and it's all set. So smooth. (I sound like an ad, but internet pinky promise no affiliation)

https://relay.firefox.com/ may be a tool for that. I never used it, as I use a catch-all, but may use it in the future.

Apple and Proton Mail both let you do this without the plus sign. You just have to generate the alias through their password apps.