The MTP protocol is notoriously slow, as it will not multiplex block operations unless traditional filesystems, and will not be able to process multiple files in parallel or asynchronously, which means the software can only check one file at a time.
So Filelight can probably handle it, but it will be highly inefficient and that would explain why the software appears frozen.
Oh, I didn't know that! It would kinda makes sense now that you say that, but I'm not too sure about this, the system resources taken by the app seem like they don't change at all when I start the scan and it's impossible to abort it (actually, I can't do anything, not even close the window, only terminating the app works).
If this is an actual issue I should probably report it, maybe there's more tests I can run?
Otherwise, do you know if there are similar apps (either GUI or CLI) that handle this better? Better in the sense that maybe it's still really slow, but, well, not freezing at least lol.
Or if I just have to find something to use on Android directly, like SD Maid
Yes it is, I dont know the technical details but KDE tends to freeze a lot. I dont know if it is impossible? Why cant apps just have a UI that always works, and the process may freeze doesnt matter?