I'll reiterate a comment I made elsewhere in this thread. With my vision corrected, 4k at 24" (~190ppi) needs subpixel rendering for crisp fonts. I would expect 5k at 27" or 6k at 32" (both around ~215ppi) would be the same, so my only option for comfortable external use with a Mac is really 8k at 32". I know that I am an outlier as I get my vision corrected with glasses/contacts to better than 20/20 (outside that 5%-95% group I guess), but I was perfectly well served by subpixel rendering (and continue to be).
Luckily, Mac is only for work, and it is passable with 32" at 4k, but I can use Linux everywhere else for much nicer fonts. Unluckily, work is 8+h :)