Got an HTPC running Mint.
$ cat /etc/os-release
It has a TV connected via HDMI. Prior to the update if I rebooted the machine via ssh it would start fine while the TV was off. But I did an upgrade:
sudo apt-get update && sudo apt-get dist-upgrade
now it won't boot unless the attached TV is on. This is why I am always reluctant to update Linux, things tend to get broken.
Just so it's clear, this isn't headless, it's just headless some of the time (when the TV is off). How do I tell it to boot whether it has a TV attached or not? This was working until the update. So something got updated and broke it.
The 2 answers here were not the fix for it. I suspect it has something to do with Grub or Wayland but I don't want to mess around with that unless I am positive I'm doing the right thing.