I would go even farther than Fizzygoo. There is nothing to indicate Elven articulation organs are any different to the ones humans have. I think we have at least not read anything of that kind in any metahuman description text so far whatsoever. Therefore, it should be exactly as easy or difficult to speak for a Human than it is for an Elf. Or'zet has that problem - it is a language for speakers having tusks. But Sperethiel does not. As such there should not even be a "non-elven accent". At most there should be a non-native accent, but those would also apply to Elves who learn Sperethiel as foreign language, or in adult life. As for Orcs and Trolls, well, they seem to do just fine speaking normal human languages so even with different jaws and with tusks etc. they should also do just fine speaking Sperethiel.
The only problem should really be to find a tutor or a linguasoft, as has been said. This is really 100% a cultural, not a racial issue. And even that should not be too difficult. It is the official-ceremonial language of Tir Tairngire after all - even though most of its inhabitants cannot speak it, so there must be linguasofts for it. And if it can be slotted into an Elven brain, it can also be slotted into a Human/Dwarven/Orcish/Trollish brain. And there are enough exiles from the Tir, especially in Seattle, that Sperethiel knowledge circulation outside the Tir should be warranted, and that one could find a mentor. Probably does not even need to be a Tir native. Hell, any player character speaking the language can try to teach it to other player characters! It is not really exactly a top secret language...