A trackback to my previous posts on ways to get literature discussed the authors inquiries to German universities about walk-up access. Walk-up access is just that, a non-affiliated person showing up in person at a library and having access to their subscriptions. The vast majority of our licenses do actually allow walk-up. Of the STEM things, the main outlier is SciFinder (Chemical Abstracts). It does not allow walk-up.
Thing is, I work in a research lab and in 2009 we moved behind the barrier so we do not have any place unaffiliated people can use our access. So I really haven't kept up with how hard or easy it is for people who are actually able to physically visit a research library.
I asked on one of the current incarnations of LSW (Library Society of the World) on Mokum. The responses were a pleasant surprise. Most had easy walk-up access. Some had computers that didn't require a login whereas others provided short term logins. Printing can be paid for in cash.
One of NYC librarians said her library charged people to get access to the building at all! Clearly not a land grant institution. Another librarian is in a place where there have been multiple shootings in the actual library building. Completely understandable that they are locked down now.
Overall, at least this access does still seem possible for people who live somewhat near a research institution, particularly if it's a public university.