This worked for me (at least for now), based on @dmbutler’s fix: Select “Block all cookies” (under Additional Settings > Privacy and security).
Then the cookies that were previously showing up all disappeared (I didn’t even need to delete them one by one).
As of now, the setting has remained that way even after I changed the Privacy and security settings back to “Block third-party cookies”.
I hope this helps, and thanks @dmbutler . But yeah, disappointed that this was an issue to begin with.