Also, what I understand from @megavolt:
…is that the problem isn’t with SDDM, or possibly even KDE. And the fact that login also doesn’t seem to work with Wayland, looks to me that it supports thee theory…
If something is removed from AUR, it won’t uninstall it from your PC. Even your output shows missing “AUR” where packages don’t exist there anymore. Besides, you can check version numbers - manjaro-firmware is from 2016 apparently. 
Only thing left from my post: what about starting plasma service with new user?
Just goes to show, I don’t use 'em much.
Just came from there. Once again, I was unable to log in. And I tried more than just F5…Seems the keyboard was still cold and stiff earlier…
Since it seems to be getting stuck on the splash screen try disabling that and see what happens;
$ cat ~/.config/ksplashrc
[KSplash]
Engine=none
Theme=None
@anon51566685 this is the best I can do. Looking for more logs now.
Accompanying boot log: https://0x0.st/Hebd.txt
And the output of journalctl -xb -1 --no-pager: https://0x0.st/Hebn.txt FWIW
I read the whole thread and I reacted to one thing.
tty1 & 2 seems broken to you but tty5 works?
As of rescent, for some reason, the tty has moved from 1 to 2 on my computer and my tty1 is frozen at boot chatter.
Could that be related?
I read somewhere in your logs it is logging in to seat0.
If you switch to tty5 and login, what does loginctl give you?
That’s not quite right.
What is happening on all TTYs is that my keystrokes gets repeated. It worked once, early this morning, so I suspect it was a fluke, or my keyboard was still cold and stiff, to slow to repeat schtuff.
Tried this just now, but it just causes a black screen where nothing happens instead of a splash screen where nothing happens.
Here is the boot log from that anyway: https://0x0.st/Heco.txt
So it eliminates that possibility, at least.
Another stupid thing I have to ask, I do not believe it would help, but it seems you are desperate for any kind of idea so here is one.
What if, you disable login, ie, login automatically (skipping sddm login screen), does that change anything?
Edit
And at the same time also disable splash like MrLavender suggested.
Edit 2
This might sound even more stupid, but have you “tried to turn it off and on again”. meaning, have you tried disconnecting/reconnecting your keyb after changing tty and see if it still prints double characters?
you
I haven’t yet, but I’m willing to test it if I can set it up via CLI from chroot if I can get the commands/config file…
Edit:
See
I added this after your comment so I repost it, sry.
Easier said than done, being wheelchair-bound and unable to get near my keyboard’s USB plug. That’s why I spent good money on a good quality keyboard - so that there’s no real glitches or so.
Damn, I knew that but forgot about it, I’m so sorry!!
Just out of curiosity, is it a mechanical keyb?
I have heard about those sometimes randomly printing double characters, but this happens ONLY on tty console correct? It most likely has no correlation here. If you are curious about what I mean, this thread is an example.
I really hope someone can help you fix this, I want to learn what is wrong too!
Edit
Don’t start digging into the keyb thing, I was just curious.
Yeah, it’s the Corsair CORSAIR K68 RGB Mechanical Gaming Keyboard. And yes, only in the TTYs, no other place.
Never mind and forget that and all those logs. Should run it just with
startplasma-wayland # or for xorg: startplasma-x11
and post logs of that. Also, you should create a user with home dir.
I won’t. I just very quickly skimmed, and it seems cool. I’ll have a look when I get my PC back.
1 Like
Accompanying log output: https://0x0.st/HecV.txt
And I’ve got to be off, my day is just about ending this side of the world. So, so long and thanks for all the fish!
1 Like
Again,
Just an advice; don’t use journalctl -x, it just pollutes everything with useless info. 
please try the propietary nvidia-driver. your card is still supported at the 5xx.xxx driver. this nouveau driver is a nightmare that cause malfunctions anytime,anywhere and especially anyhow.
the message after you started startplasma-x11 “Display is not set…” is a strong indication that the gpu cannot be initialized.
Terribly sorry. It was a long day.
ANYWAY
Saw yesterday that there was no home directory for said user, and created it just before going to bed. This morning, tried going to TY5 again, logging in with my new test user, and running
startplasma-wayland
…and it worked.
startplasma-x11
…gave me an error that $DISPLAY wasn’t set, yet I never unset it…