Hi Ged I have the beta from the Play store. The latest version is full of bugs. That's what brought me here actually. I don't want to lose the play store beta if I uninstall it as the beta program is now full and you can't install it from the Play store anymore.
Is this the same app and just a newer unofficial version?
I didn't know that the official QuickPic app was currently in Beta. However, if you uninstall it, you can always re-install it later, but you will, unfortunately, loose all of your app configuration settings
There are two ways you can do this...
Prior to uninstalling it, make a backup of your current official QuickPic APK with one of any number of APK backup utilities available on PlayStore. Some Android file managers, such as X-Plore File Manager or ES File Explorer also have the ability to backup currently installed apps/APKs to your devices internal storage for possible later reinstallation.
Or alternatively, you should be able to re-install it via this direct PlayStore link...
Uninstalling your official QuickPic app will NOT exit you from the Beta group. You have to explicitly leave the Beta group, and simply uninstalling the app does not do that.
You can always check your Beta testing status via this browser link whilst logged in with your Google credentials...
The reason why you're getting the 'app not installed' error message, is because you can not have two apps with the same package name installed at the same time, namely 'com.alensw.PicFolder', so you'll have to uninstall your official QuickPic app before you can install this modified version.
I hope this clarifies a few things for you.
EDIT~ Additional & Advisory. As @funkenwerner has alluded to above with his link, maybe the official QuickPic app just isn't worth it anymore! Cheetah Mobile have become notorious in recent years, with a dark cloud of suspicion hanging over them, regarding exactly how their apps behave and with dubious data collection practices rumoured to be occurring & potentially involving QuickPic. There are better and safer alternatives available, not least this 'modded' version by WSTxda. I would strongly advise you uninstall the official QuickPic and forget about it, and replace it with QP Gallery instead.