I have my own domain and operate my own email server with rule-based localparts filtering (basically regex-based whitelists and blacklists, plus automatic sorting into different mail folders based on localparts). I use a different localpart for each online shop and each service/social account/mailing list I’m registered with.

There are email providers that let you use your own domain (i.e. you don’t need to operate your own email server) with any number of localparts, i.e. a catch-all (without needing to use “+”), and which usually also allow you to set up filtering rules, and let you auto-forward to a different email address (e.g. GMail) if you like. You can then use whatever@yourdomain at your whim, without having to first register the localparts you use.