We thought about this a lot, and this was our approach/options.

1. A site could have content that is always free – free + premium sections (which can still have freebies post-login). This is the discretion of the site owner – something that we did on our mashingmonsters site (which makes fun of NFTs).
2. Have premium freebies not require login as you mentioned... but that would require anonymous login/tracking (e.g., google solution), which notoriously doesn't work well and is beyond invasive privacy wise.
3. The approach we took... one thing to keep in mind, is that if you are logged in on one site, next site you go to, you are already logged in, so the friction is somewhat removed (same device/space that is).
4. We couldn't think of another compelling solution.