Ikaarans are a species native to the Delphic Expanse, encountered by an alternate version of the Enterprise NX-01 after it was thrown back into the past (2037) – see the episode “E²“. That version of Jonathan Archer married an Ikaaran that he rescued from an anomaly, and their descendants are part of the generational ship Enterprise. Karyn Archer is an Ikaaran and first officer aboard the generational ship. Ikaarans seem to be a friendly species, as shown by their willingness to join Archer’s crew. Also, they seem intrigued by anomalies, and may have an affinity to them.
They may appear in any era, and as they haven’t appeared outside of one episode of Star Trek: Enterprise and only in the context of an alternate timeline, they are very open to the interpretation of the GM. It is likely that they would have joined the Federation early.
I don’t really watch Enterprise all that often, so I forgot about this species. I’m glad that I was reminded of them!