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:
They are also forcing it for regular reddit. I get a pop up and when closed you can’t scroll. There is even a thread about what to put in ublock to work around it.