Hi, before I further investigate this with either GOS forum or Proton support, I’d like to know if other Proton users also encounter the same issue on Android.
I’d like to start uploading my contacts to Proton Mail per their instructions here. But somehow, I can’t find the option “Upload device contacts” on my Proton Mail app.
Not sure if this is due to their app or because of GOS. Anyone has a similar issue?
I don’t find that option either on GOS, on Proton page it seems it’s on iOS?
Yeah the screenshots imply iOS, but I double checked the article that it didn’t specifically mention that it was only for iOS 
But thanks! I’ll reach out to Proton in this case.
An update from their support: TLDR Android isn’t supported yet.
Hello,
Thank you for contacting us.
Unfortunately, for the time being, it is not currently possible to sync your Android device contacts with your Proton Mail account, as well as to upload the contact manually from your device to your Proton Mail account.
However, this is a requested feature, and our team is working to implement it for the Android app in a future update.
At this time, we can not speculate on a timeframe when the feature will be implemented, and we ask for your patience regarding the matter.
We sincerely apologize for any inconvenience this behavior may cause in the meantime.