Yes.
I just tested it. I have a LAN connection between my cell and PC. Here is what you need to do:
The cell phone has an “Internal” IP address. This address won’t show up in Android settings. I found it using the Google Play app “IP Tools:” It will also be the default gateway for the Windows Ethernet adapter once USB Ethernet Tethering is enabled.
Connect the USB cable between phone and PC (Mine is running Windows 11).
Go to Android Settings/Connections/Mobile Hotspot and Tethering/ and enable USB tethering.
This will assign a new IP address to a new Ethernet network adapter in Windows. There will be a non Internet routable IP address. Open a command prompt and run “ipconfig”. Look for the new Ethernet adapter that starts with 192.168.x.x. Mine starts 192.168.237.x. The “default gateway” will also be the “internal” IP address of the phone.
On Windows, in the Syncthing admin console, in the remote devices area, locate and Edit the settings for the phone. Go to the Advanced tab and change (Temporarily) the “Addresses” setting from “Default” to “tcp://192.168.237.x”.
This will tell Syncthing to use the phones “Internal” IP address as the location for Syncthing running on the phone.
My Syncthing installation needed less than a minute to begin the connection and start synchronizing files between windows and the phone. I had over two gigabytes of data that needed to be synchronized to the Computer from the phone. it moved over very quickly as it should have because it was going over the USB cable.
In the Syncthing admin console, my phone shows up as “TCP LAN” in the Remote Devices area. Not WAN as it did with the address setting set to “Default”.
When you’re done synchronizing you can change the IP setting back to default or you can leave it that way if that’s the only way that you’re going to use it.
I hope I covered everything. Let me know if you run into trouble replicating what I did successfully to test your configuration.
Perhaps someone else can convert these instructions for someone who is using Linux on the PC. I’m not aware how to Ethernet tether a cell phone to a Linux machine.