It is curious, to say the least, that you who defend email privacy so much, do not allow push notifications on android if google services are not installed.
It is certainly known that google reads push notifications from your application (and all the others), and the fact that your application requires that Google is present, gives food for thought.
They must understand that more and more of us do not use these services, and the fact that this is so, only leads to think of some collusion between Protonmail and Google.
Cosnpiranoias apart I understand that this is not a functionality that can not be implemented.
On the other hand, I don't know why there is no version of protonmail bridge for android and it is necessary to use its client if at all.
Thank you for your attention.
Best regards