Start using +1 addresses when signing up for stuff.
Most email systems support them.
Let’s say you were signing up for Pelican.
Instead of
scott@domain.com enter
scott+pelican@domain.com
Any emails from pelican will come in as that address and your providers system will route it to
scott@domain.com
Set a rule in your email client to move all email containing pelican in the address to a folder which you’d logically name pelican
Here’s the good part, when you start getting spam at the +1 address that’s NOT from pelican you know they are selling their list.