@p2kle - Yes can - but not must!.
A lot of apps work, but microG does not guarantee 100% compatibility with G°°gle Play services Android. Ultimately, the user only has certainty when he installs his desired applications on his device and tries out the functionality. This is the same with other Custom ROMs.
Note: Galaxy S10 is currently not supported by /e/ OS.
These S9 models are (currently) supported by /e/ OS: Samsung Galaxy S9 - " starlte" : SM-G960 F / F/DS / N [Exynos].
These S9 models are not compatible with /e/ OS: SM-G960 0/DS (Dual-sim) / U (USA) / W (Canada) [Snapdragon]