I also made my own variant recently. I really liked the idea of litmaps but I didn't really like the UI/UX or "graph expand" feature (it uses some internal heuristic that is not very clear).

https://paper-explorer.aziis98.com/ (also on github https://github.com/aziis98/paper-explorer)

This uses OpenAlex as a source of articles and to let you explore the citation graph of papers. This is still a prototype mostly made to test out how far I could go with vibecoding (well I still checked the code now and then) something without a js framework. Someday I think I will add more features to it, but now there is already a somewhat working version of import/export so I'm fine with it.