Babylon Five? In the rec room scene ifrom ST:TMP, there was (iirc) a crewmember with a mask that covered his entire face. Must be a very isolating. If Captain Solok was able to fill his command staff with Vulcans who harboured similar view to his own, then any non-Vulcan who was hapless enough to be assigned to Solok's ship could find their lives (both on duty and off) so unpleasent and down right objectionable, that they would soon formally request a transfer. A request that Captain Solok would swiftly authorize. But only after Solok publically berated the crewmember for request one in the first place.
^ It would be very interesting to see what would happen if a human crewmember did serve under Solok's command, AND was capable of standing up to him. How would Solok react if a human underling chose to argue against Solok's treatment of humans and do so logically? Well, not exactly... Spoiler: MAJOR SPOILER The T'Kumbra is destroyed in the Borg invasion, during the Destiny series of novels. I don't know if it actually had any non-Vulcan crewmembers at that time, though.
Should it be, though? Solok has a point in that a species that's, say, wheelchair-bound or much shorter than average or perhaps suffering from dyslexia might find life happier in some role other than Starfleet frontline service, and in that the Federation is much better off if those species are not allowed to participate in its frontline defense. Similarly, Solok would have to admit that a species superior to Vulcans might be outside the parameters of ideal Starfleet cannonfodder, and might be destined to, say, rule the UFP or do its cutting edge research. But such segregation only extends to one narrow area of life, the practicing of a profession. Does this really detract from the equality of a species? Bajorans had found a caste system so perfectly workable that they apparently stuck to it for hundreds of thousands of years - the ultimate proof of concept... Timo Saloniemi
I'm assuming this is a joke, right? Were they ever admitted to Starfleet? I don't know of any extended fiction which revisits The Savage Curtain, but I was going to do so in my show so it would be good to know.
They were able to clear a relatively large area of the surface of their world of the sea of lava that was once there. And cool that area pretty quickly. This is (or could be) an indication of a technological society. I assume that Lincoln and the others were actually Excalbians who had changed form somehow, or then articial constructs. Provided their material science was advanced enough, they should have the ability to construct ships. Become a Federation member by the time of TNG? Maybe. Perhaps they could serve along side Hortas'.