@ralxx, I was curious about your issue and decided to do some testing.
All three failed for me also on /e/. Using MatLog I recorded the crashes. The main culprit being this…
Caused by: java.lang.NullPointerException: Attempt to invoke interface method ‘com.google.android.gms.cast.framework.zzp com.google.android.gms.cast.framework.zzj.zzac()’ on a null object reference
Doing some web cross reference I see that microG doesn’t quite gel with that Cast Framework requirement. There’s a big BUT here though. Decided to also try those apps on other devices with microG, five ROMs from KitKat to Oreo. The apps run fine on ROMs using the modified and regularly updated microG from nanolx/Setialpha (NanoDroid) on three ROMs. The apps fail with the official microG on two others.
Both are at v0.2.6 but the main difference is that the modded/patched microG attempts to stay in line with Google Play Services versioning. That helps with those annoying prompts about AppXYZ won’t run unless Play Services is updated. Granted, we’re not seeing that kind of behavior but I believe it’s an “age” thing. The official microG hasn’t been updated in awhile so it mimics a somewhat older version of GServices. Good news is that the main (only?) microG dev, mar-v-in, is active again. Hopefully we’ll see a new core that’ll make its way into /e/.
On a side note, that Fip app is pretty cool. Nice eclectic mix of music. Not sure why it’s twice the size of the other two and uses/needs camera permission though.