I'm really sorry it took me this long to respond.

- Try with a clean config.

With the binary downloaded from http://quakespasm.sourceforge.net/download.htm it happens with a clean config too.

- try the Linux binary from http://quakespasm.sourceforge.net/download.htm as well as the Ubuntu one you can install with apt. Does the issue happen on both?

Ok, I've installed Quakespasm via the Software Centre or whatever it's called nowadays (which I guess is the same as installing via the terminal with apt. It's called "quakespasm-beidl", though. Is that right, or did I accidentally install the wrong thing?). As far as I can tell, the problem doesn't happen with this version of Quakespasm, or at least it hasn't yet.

- Type "condump" and upload the resulting file

Should I do this for both versions of Quakespasm I now have on my computer? And where do I upload it?

- Do you get a reasonably good framerate? What does "host_maxfps 1000" then "scr_showfps 1" show?

Under both versions of Quakespasm, my framerate is initially just under 200 on the start map and then rises a little, while hovering between 200 and 300 on e1m1. Is that good? The version downloaded from http://quakespasm.sourceforge.net/download.htm seems to have a slightly higher framerate, though, for what it's worth. 

https://snapcraft.io/quakespasm-beidl 

It would be nice to be able to bind my own menu navigation keys in QS. My keyboard doesn't have regular arrow keys but can send the numpad direction keys. Is this feature already present and I just don't see it? It's not super annoying to have a second keyboard shoved in the back of my desk to do Quake menu nav, but it would be nice to use my aircraft carrier Model F for everything. 

Oooh, Model F, you say? o: Gotta love dem clicky keys! ;) I'd wager some hardcore typists would pay a hefty penny for one of those keyboards. :D 

I love my Model M keyboards. 

Condolences to anyone else in the same building as you when you're typing on that thing. 

where does one buy these? 

why does the Quakespasm still have that "skin is taller than 480 issue"? At number of other engines have took care of that, why can't Quakespasm? 

Version 0.93.2 of QuakeSpasm is released.
Changes since the previous version:
https://sf.net/p/quakespasm/news/2019/11/quakespasm-0932/
Downloads:
https://sourceforge.net/projects/quakespasm/files/
http://quakespasm.sourceforge.net/download.htm 

... please? 

what is the command to disable fullbright in the quakespasm engine? 

... in the console.

Posted in the vein of "give a man a fish" VS "teach a man to fish". 

got it. Thanks! 

After finding much success with EZQuake and 3620x2036 DSR enabled via NVIDIA settings I notice that QuakeSpasm cannot handle the DSR resolutions well: the console rendering gets all whacked. 

Define "all whacked"
I can run it in 7680x4320 and it looks just fine.
Have you tried changing scr_conscale? (also scr_menuscale, scr_sbarscale) 

Well, this is odd: I tried to take some screenshots to show exactly how it is "all whacked" only to realize that screenshots in fact show the console and the entire screen rendered correctly. It's only on my actual screen where things look wrong.

As I started paying more attention I realized that going above the screen native resolution of 2560x1440 increases the overall "zoom level" of the screen. When using DSR resolutions, I can clearly the the bottom "status bar" dissapear and the left side of the console window falls outside the viewpoint. As the DSR resolution is increased further, so increases the amount of this "zoom" leaving out borders of the screen out from view.

Are there some other cvars involved? 

Apparently QuakeSpasm was trying to used windowed mode instead of fullscreen. 

Setting cl_bobcycle to "0" makes the screen go grey.
Found this out after a long battle to get things to work again. 

Setting cl_bobcycle to "0" makes the screen go grey.
There's a division-by-zero in the original code with cl_bobcycle 0 - "cycle = cl.time - (int)(cl.time/cl_bobcycle.value)*cl_bobcycle.value;" - whether or not it makes your game go nuts probably depends on compiler options/etc and unfortunately in the original engine it was OK but in some ports it's not.

So just set it to a really low value until the QS devs fix it. 

I think the intent was "cl_bob 0", not bobcycle 

I had an config file which works good with many engines. At some point though I only got this grey screen in quakespasm. After finding the solution I wanted to post here to help anyone experiencing the same problems. 

Yes, "cl_bob 0" is obviously the intended way to disable bobbing in the engine, but unfortunately "set cl_bobcycle to 0" is one of those items of "Quake lore" that gets passed around, which accidentally works some of the time, but which is actually wrong.

Fortunately it's an easy fix in the code: just check if it's 0 and set cycle to 0 if so: https://github.com/id-Software/Quake/blob/master/WinQuake/view.c#L117 

So, I woke up at 3am, bored, and well here's this..

https://youtu.be/2SABwkUnqRE

in r_alias.c

i just added the shade variable in GL_DrawAliasShadow
after..

R_LightPoint (e->origin);

shade = (((lightcolor[1] + lightcolor[2] + lightcolor[3]) / 3)/128);//R00k

//then

glColor4f(0,0,0, shade * (entalpha));//R00k: fade light based on ambientlight

//before

GL_DrawAliasFrame (paliashdr, lerpdata);