newpipe can play offline files I'm pretty sure

there is an ffmpeg flag to skip silences though it hasn't worked all that well for me. I don't know whether any audio player apps try to use it. In the worst case you could do something awful like run ffmpeg on a PC or under termux to make a new audio file with the silences removed, and then play that under some other app.

I don't remember whether rockbox had that feature but I think efforts to port rockbox to Android eventually stalled due to technical obstacles. No idea whether newer Android versions could help with that.