A bit of trial balloon here: in an obscure paper from the 1970s, Japanese astronomers took red/far-red plates with the Kyoto 40cm Schmidt, and published a list of 55 'extremely red' stars in the region of the Orion Nebula. No spectral types were determined, but I have gone over the list and estimated new types by examining the GAIA3 spectra for the stars, All but one of the stars appear there, though in some cases the types are more-or-less indeterminate. The missing star probably results from plate flaw(s). I have copied the list here:
https://ftp.lowell.edu/pub/bas/starcats/oi77.dat
The source paper is not available on-line, and is not indexed in SIMBAD, though there is an ADS entry. I got a pdf from Lowell Observatory's wonderful archivist, Lauren Amundson, presumably through some secret librarian back-channel. The authors' intention was surely to find low-mass Orion T Tauri stars, but there are very few in the list. Nearly all are background M-giants, semiregular variables etc around the periphery of the star-forming region. A couple of foreground M-dwarfs appear. I identified a new S-type star in the list, a nice addition to these uncommon stars. The great majority are once/future variable stars, so the types should help in classifying the lightcurves.
\Brian