So much of this is subjective / a matter of taste that I think your best course is to try for yourself: for every reasonable paper option you can identify, buy a small letter- or A4-size pack. Pick out a few sample images and print each of them on each paper. Label the paper on the back with a pencil. Do a viewing comparison and see what you think / like.
But to try to answer more directly, if I understand correctly, you want:
* less glossy than traditional luster, satin, and pearl surfaces;
* but more glossy than traditional matte;
* either cotton or alpha cellulose base, but not RC;
* wide gamut; and
* (for archival properties) no, or no more than minimal, optical brightening agents.
Just a couple of years ago I'd have suggested Hahnemühle Photo Silk Baryta, which is probably closest to the surface you seem to want, 100% alpha cellulose base, and low (but not no) OBAs. There were multiple other papers that others believed were at least very similar and maybe the same, Ilford Gold Fibre Silk and the original (not version II) Canson Baryta Photographique being maybe the best-known. But the company that made these papers lost the ability to do so, and they were all discontinued.
Some people think the best available somewhat-similar paper is Moab Juniper Baryta Rag, and some people have made Red River Palo Duro Baryta Fiber 300 sound like a good alternative, but I've never tried either.
If you can accept a bit more gloss / sheen, then Canson Platine, Red River Palo Duro Softgloss Rag, and reportedly (I've never used this one) Epson Platine have huge gamuts, no OBAs, and 100% cotton bases.
