i ended up searching huggingface's github for closed issues that mentioned 'transformer-xl'
it showed me results for other long context transformers than just that one. the most recent it showed completed i think was longt5. i didn't find transformer-xl models in the huggingface hub; it was made more difficult, since xl has been adopted as an acronym to represent large size rather than large context, so i may have missed them. but there are longt5 pretrained models. if one of them is small enough to do local inference on my system, i may be able to plug it into adapter transformers. don't know for sure.
