IzzyOnDroid and direct install will install the Proton mail app with Google push notifications. With the main F-Droid repository the maintainers will check the source code. The small team of Tutanota mail app did away with Google in 2018 https://f-droid.org/2018/09/03/replacing-gcm-in-tutanota.html And as far as I know Signal messenger app is available without Google push but using websockets.
But it is already on the IzzyOnDroid repo. And you can also just install from their github directly.
IzzyOnDroid and direct install will install the Proton mail app with Google push notifications. With the main F-Droid repository the maintainers will check the source code. The small team of Tutanota mail app did away with Google in 2018 https://f-droid.org/2018/09/03/replacing-gcm-in-tutanota.html And as far as I know Signal messenger app is available without Google push but using websockets.