when it works it's amazing. but very often both my phone and laptop are connected to the same WiFi, yet kde connect can't see them. I can't figure out how to diagnose and solve that when it happens
Agreed. I've read a lot of apologetics for KDE Connect but there's definitely something wrong with discovery. Often it will fail to discover other devices unless I click "refresh" in both devices. I've gone as far as writing a script to force-refresh at 1 minute intervals. Sometimes it can't be persuaded to work at all. Blame my network maybe, but LocalSend works every time.