I’ve been using this application for about a year and I am amazed at just how powerful it is for my needs. There was a bit of a learning curve, but it’s one of my favorite apps now.
This does not look to be open-source. The webpage lists open-source licenses for the libraries used by this app, but there’s no open-source license for the app itself.
And while there’s a GitHub repo, it’s empty. It seems to be used just for hosting the APK files.An open-source app with decent editing capabilities is Fossify Gallery: https://f-droid.org/en/packages/org.fossify.gallery/
I can’t find an F-Droid build. When I start the app I get one of those large consent banners, when saying I don’t want cookies that have “legitimate interest” the app tells me it cannot run without ads.
I don’t think, it’s open-source…