A hint in this sea of ​​information

[Hardcorized]

Hello everyone
I'm a real newbie on the subject, I've tried to experiment in the past by tinkering a bit but I've never managed to get my head around this world in a more advanced way.
I found this forum almost by accident that seems to answer my questions.
I've been trying to download a drm-protected video for months but I'm stuck at one point. Using N_m3u8DL-RE, ffmpeg and mp4encrypt I finally managed to download the video but it can't be seen or heard.
I can find the KID of the video but without the KEY it's not possible to decrypt it.
I've tried to look at several threads but with my limited skills I'm not sure if a particular thread could be what I'm looking for.
Who can help me by indicating a guide for what I would like to do?

Thanks to everyone in advance.

[Obo]

The guide is here: https://forum.videohelp.com/threads/416316-%5BRelease%5D-WidevineProxy2-Extension-Bypa...s-Lic-wrapping
Probably missing piece is here: https://forum.videohelp.com/threads/413719-Ready-to-use-CDMs-available-here
Or maybe better here: https://forum.videohelp.com/threads/417425-Real-Device-L3-Cdms?highlight=wvd