One can try ssh (which is enabled by default) with root/1234 (default), or the Debug TTY. This does exist on the NanoPi R6S between the USB-C Power and HDMI port. There are no headers soldered on, so that has to be done first with headers that can be purchased at one of the following URLs.
Once the headers are one, you can connect to this port with a USB to UART device (preferably with a chip such as the CH340C, CP2104, FT232R) connected from another Windows, Linux or Mac computer. I suspect this device will work.
https://www.amazon.com/gp/product/B07BBPX8B8
Debug TTY instructions are located here:
https://www.youtube.com/watch?v=UpVMO7gbnYM&t=226s
Chad Skeeters got a reaction from laibsch in No display when trying to install Minimal Trixie on R6S