You are experienced terminal user, like me.
The reason why I use the GUI in the example is to show you can still do stuff with the root gui, if one is a gui person and comfy with it.
Yes nicer to use cli commands for this. Agree 
The main thing i think is . Switch kernel and see what happens. 
My bad, didn’t see the edit. Either way, i tried that now, but it didn’t work.
Which part didn’t work? Please be more specific.
As an aside, we know next to nothing about your system, other than that you’ve got an Nvidia adapter. But we don’t know what filesystem you’ve got, whether it’s btrfs or ext4, whether your drive is encrypted, and not even whether it’s a desktop or a laptop.
I’ve only just spotted this now. No, this is not correct. 
When you install ventoy to a USB stick, it does not allow you to choose between UEFI or BIOS, because it will boot from either one. What it does allow you to choose is whether the stick will be partitioned as MBR or as GPT.
Why not the first advice you gave at the beginning.
No need for more info.
This looks difficult and things are not going as expected.
It is so easy to reboot into another kernel.
respect 
Which part? I’ve provided so many different approaches.
The problem is that the OP apparently cannot boot from a USB stick anymore, and they’ve messed up their privilege escalation via sudo. So the only way into their system anymore would be a root login in single-user maintenance mode.
Yes, but that won’t fix the screwed up permissions and ownership of the sudo executable and configuration file.
Yeah, sorry for giving so little details, i thought the issue would’ve just been about the drivers.
Anyway, I’m on desktop, i have an ASRock mobo (thought i mentioned this before). B550M-HDV to be precise.
My filesystem is ext4, and it’s not encrypted.
About this, i don’t really know what else to add. I managed to open maintenance mode in the way you suggested, and ran those commands as root (which, btw, couldn’t i have done that just by logging in as root from the ctrl-alt-f3 menu?), and then rebooted, but the sudo still doesn’t work. When i ran those commands though, i didn’t get any feedback, so maybe that’s telling?
About this, I was about to try this, because i noticed that ventoy has MBR partition as default, but GPT is suggested for my mobo. Should still try yes?
UPDATE: that didn’t work. Still gives me RTK as the only USB boot option
Yes, if you could log in as root, but that was not a given. Many people don’t set a password for the root account during installation, and then you cannot log in as root.
If you didn’t get any feedback, then the commands were successful. They will only give you feedback if they fail.
Either way, you can verify whether it worked or not by running that command I gave you very early in the thread… 
for f in /etc/sudo.conf /usr/bin/sudo ; do ls -l $f ; done
GPT bears preference if the system boots in native UEFI mode, but for a USB stick it shouldn’t really matter, unless your UEFI has a bug. Normally, a decent UEFI should be able to boot from an MBR drive either way.
Oh, great! The command shows root is owner now, so at least that part is fixed. Issue is, i still can’t use sudo commands or enter su -…
Well, that’s why we need more information. What else did you change?
su isn’t even related to sudo, so you must have changed a lot more. Did you mess around with PAM? 
Well, I don’t really know what I’ve changed either, that’s the issue 
All I know is, I was trying to change ownership of the drivers management from the root to my user, so i wouldn’t get the polkit issue, but i ended up dragging a lot more stuff with it. Is there maybe logs i can pull up from somewhere? so i know exactly which commands i used (i don’t think i used anything other than chown though, no idea what PAM is)
Well, there’s your bash history as a possibility, depending who you were logged in as.
It won’t be in the logs, but if you did it via the command line, then it might still be in your shell history.
But if you messed with the permissions on the drivers as well, then who knows what else you may have messed up.
And considering that you don’t have any means for booting from a USB and no backups, the perspective is becoming rather bleak… 
That is a classical tell when it is a time to reinstall. And for your next try you know: backups and taking notes of what you change.
p.s.
UPDATE: that didn’t work. Still gives me RTK as the only USB boot option
Test it. Usually it has to be called Ventoy, but some bioses just show the controller name or id or serial. It does not really matter, if it is the only new device that appears after you plug the usb in, then this is it.
A little late in the flow, but for general and future reference:
Alright, update on everything:
I managed to get the USB to work. First, i reset my UEFI settings to default (just in case), but it still wasn’t working. I then tried to use the USB on a different device, to check if the USB was the issue, and it worked, i could easily install Manjaro on that device. With the ensurance that it wasn’t the USB’s fault, i tried booting my pc with it again, and, in a process that can only be described as somehow, it worked. My guess is that booting it through another device somehow made it applicable to my pc again(?), but i really have no clue, this is just speculation.
With that, everything else got fixed: i just reinstalled Manjaro, so no permission issues, and now i have the correct drivers, and no more polkit issue since i’m on the most recent kernel.
Thanks to everyone that helped, and sorry if a lot of what i said was confusing, but, like i said, i still don’t really know how i managed to even fix the whole thing, much less what the actual issue was.
Possibly something as simple as re-seating the USB.
Occasionally, I find some USB drives need to be positioned “just so” otherwise the contact isn’t reliably certain. Generally this can be attributed to design or manufacturing flaws – some USBs fit too loosely in the socket.