Steps to achieve a working state for SSH

Backup stock SD card, do not format it yet
Download the UnofficialOS image for R36 clones and follow these instructions. Other OSes might work, but take note that if your device comes with ArkOS as stock, you will need to generate a compatible DTB file which works with non-BSP OSes (see Links/Resources for BSP vs non-BSP Linux builds)
Check that you can boot into Linux and have working D-pad and button controls (you should load into EmuStation after about 1 to 2 minutes of booting up). Depending on your requirements, you might want to ensure the analog sticks are working as well.
Ensure you have a working USB OTG dongle/cable. Plug it into your device (specifically for RX6H, it is the HOST port and not the DC/OTG port). If your device is supported OOB (typically WiFi 5 and older), then you're in luck!
In the default EmuStation application that launches, press START, go into NETWORK SETTINGS menu option and under the NETWORK CONFIGURATION section, select ENABLE NETWORK.
Select WIFI SSID to search for your wireless network and connect to it (by setting the WIFI KEY in the previous menu)
Scroll down the main NETWORK SETTINGS menu and under NETWORK SERVICES, select ENABLE SSH. The default SSH password can be found in the main settings menu under SYSTEM SETTINGS, AUTHENTICATION section.

Links/Resources