@Roxas84 Does your notebook have an Nvidia video card?
I can't be sure, but, researching about it, I only see users who use Nvidia graphics cards reporting "HDMI1 disconnected" problems (on Linux, I didn't find a similar report here on the forum, but Recalbox is based on Linux, comparison), see:
https://forums.developer.nvidia.com/t/hdmi-output-missing-in-xrandr-command-and-external-monitor-does-not-work/68011
https://forums.gentoo.org/viewtopic-t-1090914-start-0.html
https://unix.stackexchange.com/questions/81822/hdmi-not-detected-by-xrandr
https://forum.manjaro.org/t/xrandr-says-hdmi-is-disconnected-for-external-monitor/28445
https://www.linuxquestions.org/questions/slackware-14/xrandr-reports-hdmi1-being-disconnected-when-it's-connected-4175479547/
I can't tell you that any of these solutions work in Recalbox, probably not, but you can try it if you want.
I believe your problem is a type of driver incompatibility, and if that is the case, there is nothing you can do.
But, I'm not a developer, I can't say much, the most I can help is up to this point, I don't have enough technical knowledge to help you further.
