Early this month there were great news for ProtonMail users:
In order to expand access to the privacy tools we develop (currently ProtonMail and ProtonVPN, to be joined in the future by ProtonCalendar and ProtonDrive), we plan to publish our apps on a number of alternative app stores for Android. A few possibilities are presently under consideration.
First, we plan to release our apps on F-droid, an open source Android app repository, which is today one of the most popular alternative app stores. In addition to F-droid, we are also considering a few additional app distribution channels (…)
[bold emphasis mine]
They didn’t capitalize the D of Droid 
Like Tutanota before, this is a company that knows how to treat their customers.
I love it 