Is there any proprietary Android app for which you wish there would be an open-source alternative?
Basically, what the title says. Do you use any app, that is proprietary, but either has no OSS alternatives or they're all not good enough? If there is an alternative, what keeps you from switching?
MicroG works well if you let it leak some data to Google.
I would like a free-as-in-free-from-Google Google Play Services reimplementation that lets me use any app that depends on it without hitting any Google server.
Free software (not open-source, it's really free software that's important) that depends on a single for-profit vendor is not free.
MicroG is open-source but it's not free. It fails to address two problems:
What do I care looking at the source code of a Google Play Services replacement when Google still holds my cellphone by the balls for certain critical functions?
Why do I need permission from Google for apps to function properly on my cellphone?
I don't think OP cares about getting the source of the apps they run so much as the apps being free-as-in-libre in his original question. Many people mistake open-source for free software and MicroG is not truly free.
(I reread ops question and I can only see the term open source 2 times, but whatever, I understand what you say, and I don't want to debate about semantics.)
The point with microG is it's still the best way if you want to use android. The other options are:
Play services (GMS), or Huawei has some similar solution because of US trade embragoes.
You can use android without play services but notifications won't work for most apps, even if you can open them. (UnifiedPush tries to solve notification part) Wifi and cell based location won't work
I see microG as an acceptable middle ground. I still have to give up something to goog, but it's not much compared to GMS, and I can use all available apps