Generally no, but if your hitting a dead end looking for things on Google/Bing based engines, it doesn’t hurt giving Yandex a shot.

I trust their privacy claims but if you backup your email and calendar you can just as easily move elsewhere if Proton does go down. Having only one provider can make things a lot easier to manage.

The easiest way is to look at your Installed apps through F-Droid as it will show both apps installed through F-Droid and apps from the Play Store that are available through F-Droid. You can copy-paste each source link into Obtainium.