Just use single-correspondent mail addresses for signing up, i.e. weirdwebsite-myname@example.org and strangesite-myname@example.org (using a hyphen instead of

Just use single-correspondent mail addresses for signing up, i.e. weirdwebsite-myname@example.org and strangesite-myname@example.org (using a hyphen instead of a plus sign to get past unhelpful mail address sanitizers), add a regex for * -myname to /etc/aliases and you're set. You don't need to set up special addresses, the regex alias will make sure the mail ends up in your INBOX. I've done this for more than 20 years without being inundated in spam, I never use my 'real' address for interaction with others than friends and family.