How can i check APK signatures on my Android device without using build-tools?

I just recently started my privacy journey and I’ve been following privacy guides to do so. The device I’m currently working on securing is an android phone. Some of the apps I’d like to download (secure camera, secure pdf viewer, newpipe and shelter) are recommended to be downloaded from their github or gitlab repositories. I’d obviously for security reasons like to check the APK signatures. So I was going to follow the guide on how to do this in the “Android recommendations” page of Privacy Guides. However, it doesn’t seem like I can install Java JDK or the Android Studio command line tools. For the former it just gives me no options to download and for the latter it says that my current device is not supported. So it seems as though I won’t be able to use this to check APK signatures. Is there any other secure way that i could check if APK files are safe before downloading them?