Sapio
Open source, crowdsourced app you can get from F-droid which is designed to track and list which android apps will or will not work on a Gapps-free Android device.
Its searchable, per-app list has separate compatibility categories for straight AOSP/vanilla ROMs as well as devices with #microG.
For each one of those categories it will show a color-coded legend:
Green - works with no limitations
Yellow - works with some limitations
Red - Doesn't work at all
You can also contribute to #Sapio by sharing your personal app compatibility experiences. The more submissions they get, the handier this tool becomes for all of us. ☺️
You can get the app here: