As a
Dane, I’d pronounce the three options completely differently, unless I’d say them in English. I’d only use
Kira (kee-ra). I think
Kyra sounds strange.
Keira makes me think of centaurs (Chiron/Keiron) but I honesly kinda like that, though.
Kira = kee-ra
Kyra = ky-ra where the Y is pronounced like the French say U or the Germans say Ü.
Keira = k eye - ra