Ubuntu login loop reappears after every reboot, how to fix it?

I tried everything here but nothing helped. What I found helped is to reinstall manually the proprietary nvidia driver(NVIDIA-Linux-x86_63-390.87.run). But only until the next restart. After that I am stuck again in a login loop and have to reinstall the drivers again. This is cumbersome and I would like a fix where I do not have to reinstall them every time. The problem seems to be that both the nvidia driver and the nouveau driver want control over something(xorg server, gpu, display)? I found this out because of this post. Specifically after running lspci -vk | grep -iA15 NVIDIA I get the line:

01:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 960] (rev a2)
        ....
        Kernel driver in use: nvidia
        Kernel modules: nvidiafb, nouveau, nvidia_drm, nvidia

This seems odd to me becaue of two things. I know I saw once somewhere a file that was created by the nvidia driver that read something along this:

# Nvidia driver autogenerated do not touch
blacklist nouveau
options nouveau modeset=0

Plus I followed this post and added a file /etc/modprobe.d/blacklist-nouveau.conf with this content:

blacklist nouveau
options nouveau modeset=0

and then I did:

sudo update-initramfs -u
sudo reboot

but the lspci line still shows the same drivers, notably nouveau being still there and the /var/log/xorg.0.log shows:

(II) LoadModule: "nvidia"
....
(II) LoadModule: "nouveau"
....
(EE) [drm] Failed to open DRM device for (null): -2
(WW) Falling back to old probe method for fbdev

Summary

• How to fix the login loop without needing to reinstall the nvidia driver manually every time?
• How to blacklist the nouveau driver?

What are not options

• Reinstalling ubuntu is not an option.

• Just using the nouvea drivers. I need the nvidia drivers.

Let me know if you need more info, e.g. the .xsession-error log.