As of a few minutes ago old.reddit.com now seems to requre logging in to access it.
Shame as it was still the best place to browse for info about some niche interests.
Edit: Seems like they might be testing the change as it is hit or miss at the moment.
Edit: Adding this to My flilters in uBlock Origin seems to fix the issue for the time being:
||reddit.com^$header=referer:
This is it exactly. It was hit or miss for a few weeks for me, some vpns would get the login some wouldn’t. Some subreddits would get the login, but comments wouldn’t.
Now it seems its all login all the time.