Hoël Bézier wrote:

However, it does wake up if I switch to another TTY (e.g. ctrl+alt+F4) and lets me log on, so it has obviously booted up. If I switch back to TTY 8 from there it just shows a blinking cursor (i.e. not SDDM, which is what I'd expect). If I reboot from the TTY that lets me log on, the boot process is usually normal and leaves me at the SDDM login.

Any tips on how to debug this would be much appreciated.

Since you can switch ttys, this means your computer “properly” booted. So as far as we know, the only culprit is your login manager which failed to start, or started improperly.

For starters you could check, once logged in, if it is actually running or not.

ps faux | less

will output the whole list of processes on your computer, check it to see if you can find sddm in the list.
If not, then it failed to start, so you want to check if the service in charge to start it has been run.

rc-service sddm status # for openrc
systemctl status sddm # for systemd

These commands should tell you if the process has been started and failed, or if it never started in the first place. If it started and failed, search for logs, or even try to start it manually. This will give you indications as to why it won’t run.

Otherwise, if it was never run by your service manager, this means something earlier in the dependency tree failed to run. Same solution here: search for logs, `rc-status` will give you the list of running services on your computer and their state for openrc.

Good luck,
Hoël

He could also do a:

ps aux | grep sddm

and see if it lists it. Replace sddm if using something else.

I'm not sure why but sometimes on my system, the GUI part is on 4. I once found it on 2. Most of the time it is on 7 but sometimes, I find it in other places. 4 is the most common alternative. You may want to cycle through ctrl alt F2 through F9 and see if it just parked itself somewhere else for some crazy reason. If you find it moves, we have a common problem. Most often it is on 7 where it should be but sometimes I have to go hunting for the thing.

I've often wondered why it was in the wrong place. I just figure as long as I can find it, better not complain to much. LOL

Dale

:-) :-)