I use MPV, VLC would be an alternative.
MPV is often preferred for being more minimal. But I dont know how the differences are on Android.
MPV has hardware decoding, which likely saves batterylife by being more efficient.
Alternatively there would be the AOSP Gallery, I also have Fossify Gallery and the recently mentioned Gallery.
Are there multiple media players that Android apps can use or integrate? I saw that MPV has support for mkv which is important for me, so media support is likely important.
Does Android use gstreamer?