I have a vague recollection of setting up mgr on Linux back in the nineties and giving it a spin. Maybe it was bundled with Slackware? That was the era that Slackware came with the Andrew user interface system and apps as well as xview.
I remember installing MGR (or at least trying to), but I couldn’t really work it out. I was only a teenager, probably my early teens.
I remember exactly where I got it from - InfoMagic’s 1994 Linux Annual 4 volume CD-ROM set. Although that did contain Slackware, I’m not sure if it actually was a Slackware package. The CD-ROM set included dumps of Sunsite and TSX-11, and I think maybe it was from one of those.
This CD-ROM set went through a few different editions, and Internet Archive has some of them, but not sure if it has the exact one I had - which I still have somewhere, I should probably try imaging it (assuming it is still readable decades later)
I never got Andrew's software working. If anyone ported them to modern systems (and made them XFT aware) they could be more known. If the current Nedit with OpenMotif compoled against XFT supports Unicode really well, why not?...