I met my nevermo wife on Match.com (this was long before the Tinder-era). My best exmo friend met his exmo wife on OKCupid. Another inactive couple friend met on a site called HowAboutWe.
They told me these sites (at the time at least) had a relatively large population of exmo/inactive singles. They would simply search 'Utah' within the profile description along with 'Atheist'/'Not Religious'/'Spiritual'/'Rather Not Say' in the Religion field!
Again, not sure what online dating is really like these days. But at the time, most exmo singles were looking to "integrate" within mainstream dating life, especially those who lived outside the Moridor.
Remember, there are numerically waaaay more of us then there are of them. You'll also have the shared experience to serve as a foundation. Good luck and have fun!