Warpinator (flatpak):
This Linux Mint-developed app for transferring files or directories over the local network works well. It’s able to communicate with your network’s other computers running native or flatpak Warpinator, and with your Androids running the ported version from F-Droid.
I’m having issues with pasting screenshots right now, but I’ll update this post with some images when it’s fixed.
See this TUTORIAL.