Sorry, but I cannot comment because I have too few points.
I've experienced this issue myself in the past with files and (don't ask me why) just editing the files with a plain GUI text editor worked for me when I saved the file.
Also the CLI text editor micro tells you Permission denied and prompts you if you want to save the file using sudo if you don't ...
I added the following kernal parameter and updated the grub.
The other options were not working for me which is what I had set in the grub after reading the arch. Replacing those with this fixed the issue.
Thank you felix for you help! :)
You can do it in 2021 but you have to install the rtl8192eu driver
But I prefer the WLAN Stick: TL-WN725N or TL-WN722N.
These two have the same chip set and are working just fine. But you have to download the driver (there are many YT-Videos ) to enter Monitor Mode.