There is an useful F-Droid app called Yalp Store which make posible to install Play Store app’s without Google services. But some app’s can’t work in my FP2 Open OS without those services. Does it exist any simple way to make them work?
It really depends on the apps whether there is a simple way or a more complicated way. See the #installanyapp guide to get some ideas. But be aware the guide wasn’t updated in a long time, so some things may have changed.