I use one called X-Plore. It's actually very good. Even has a WiFi server, conpressed archive support, etc. but the downsides are that it's close sourced and some features are behind a paywall (though IMO they are worth it).
So I was thinking of moving to some free or open source software. Any recommendations?
It's free (not sure if FOSS), and there are non-essential-but-nice-to-have features that are paid, just to support the dev - but the free features are awesome, and more than enough for me.
It's not FOSS.
FOSS means Free Open Source Software (Free as in freedom, not as in free beer).
MiXPlorer is neither open source nor licensed under a FOSS license.
It's proprietary.