ROX-Filer is still actively developed. It is the primary file manager used in Puppy Linux, EasyOS and some other distros. A couple of active repos:
https://github.com/jun7/rox-filer
https://github.com/puppylinux-woof-CE/rox-filer
This statement is incorrect: "Unfortunately, no version of Rox, either packaged or compiled directly from the source, seems to be completely integrated with the mimetype definitions of the modern Linux desktop"
Mime handling is fully integrated in Puppy Linux and EasyOS. If you want to find out for yourself, try the latest EasyOS: https://bkhome.org/news/202212/easyos-dunfell-series-version-453-released.html
ROX-Filer is still actively developed. It is the primary file manager used in Puppy Linux, EasyOS and some other distros. A couple of active repos:
https://github.com/jun7/rox-filer
https://github.com/puppylinux-woof-CE/rox-filer