Share your displaying configuration by running "neofetch" and post it here. If your X11 is running on top of framebuffer, instead of DRM, it wont work. I also would like to get more debug from cedrus, linux's v4l2... but at least you can add -v to mpv to get more debug You only need the ffmpeg plugins offered by the original poster of the v4l2-request thread This is tested with mpv player only. v4l2-util and -ctl are only useful for webcams and video capture devices. v4l2loopback is not involved here. I don't have it I have an orange pi zero LTS, but I havent tested it there (I would use an SPI LCD, since it doesn't have an HDMI prot)

For debian problems, do what I do: Get the cheapest raspberry Recreate the problem Ask the question in the raspberry forum Apply solution to Armbian XD

Oh, sorry, I didn't notice the non-existent 6 and read it as Helios64. Of course, my description of the boot method is not limited to Rockchip devices; it works on all for which a mainline U-Boot is available. I have used it on iMX6, LX2160A and S922X devices, but my remaining devices are all based on Rockchip. The solutions are too varied to present a turnkey solution here. However, I am sure that only a corresponding configuration for implementation is required to achieve the desired behavior, but for that, the U-Boot documentation must be consulted to decide which solution should be chosen.

Thank you for your answer. My board is not Rockchip-based, we have been generalizing the discussion for quite a while now. Well, and this is where it would get interesting but ...

Since the RK3399 U-Boot can use an HDMI display and a USB keyboard, I would simply configure a jumpstart option in the boot flow that mounts a different root filesystem. When booting, you just have to select this option. If interacting with the firmware console is too complicated, the recovery system can be placed on a removable storage device. In this way, in case of need, only the rescue media needs to be connected and the system restarted; no firmware console access is required. A completely firmware-controlled fallback mechanism is also possible, but it requires further special configuration of the firmware. Read this thread to understand what I mean by my statement.