In Star Trek: Discovery season 5, episode 5, “Mirrors”, Detmer and Owosekun were assigned to pilot the Mirror Universe’s ISS Enterprise to Federation HQ by Captain Michael Burnham (Sonequa Martin-Green). This explained Detmer and Owo’s absence for the rest of Discovery season 5.
However, Detmer and Owo do appear in Star Trek: Discovery’s epilogue scene, and they were a sight for sore eyes.
I barely even noticed they got replaced. They never got to have any story involvement or character development, just like most of the rest of the bridge crew in Discovery.