How to transfer files between Linux and Android in a fast and reliable way?

KDE connect. I'm transferring pictures from my phone with 35 Megabytes per second on my home wifi. At my workplace the wifi/network is considerably poorer: I only get ca 0.5 megabyte per second. Same computer - same phone.

Creating a shared wifi on the computer via the network manager can speed things up a lot. (Remember to set a wifi code so you don't open the network)

Use ADB push/pull. Or I think some devices support the pre-MTP USB mass transfer. Might need to enable it first. Though adb is probably best for large and fast transfers.