After following some guides, I was able to get a USB SSH connection working from my Windows 10 computer into my Raspberry Pi 4. It won't work on my phone though, even though my phone is capable of tethering. I've tried both the 'IP Neighbors' method and also the static IP address as recommended by the tutorials.
Scratching my head because I originally wanted to do this for my phone to be a direct-connect SSH to RPI4. It just happens to work on the desktop which I don't really care about so much.
The Raspberry Pi 4 USB-C charging cable goes to a power supply on my docking station, which is why the desktop just happens to notice the 10.55.0.1 static IP on the RPI4. When I connect the Android (Samsung Note) from its own USB-C to USB cable into the Raspberry Pi 4 USB port, then I can't connect to it with pinging or with SSH.
Here is what the Android phone says for 'IP Neighbors'
REACHABLE 192.168.42.127 dev rndis0 lladdr 5e:<all that address stuff> DELAY
Here is what's going with usb0:
pi@raspberrypi:~ $ cat /etc/network/interfaces.d/usb0 auto usb0 allow-hotplug usb0 iface usb0 inet static address 10.55.0.1 netmask 255.255.255.248 pi@raspberrypi:~ $ ifconfig usb0 usb0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 10.55.0.1 netmask 255.255.255.248 broadcast 10.55.0.7 inet6 <...> prefixlen 64 scopeid 0x20<link> ether <...> txqueuelen 1000 (Ethernet) RX packets 6971 bytes 723210 (706.2 KiB) RX errors 0 dropped 5 overruns 0 frame 0 TX packets 4143 bytes 1380280 (1.3 MiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0