My son asked for a MP3 player... so I busted out my 20 year old Sandisk Sansa 200 and updated its firmware with #rockbox
I was surprised that not only did it still work, but that rockbox has seen continued development... it released version 4.0 on April 1 of this year.
Unfortunately, to get the #appimage to work, I had to hunt down an old version of ssl (libssl1.1), but once I installed that, the graphical utility was able to detect and update the firmware.