I suggest you complement it with your own experience in practising it, as in the past,
mdayonliner wrote its version by using my thread
PGP/GPG Signed Message - Public Key in Indonesian as a reference*.
In my thread, it is intended for several OS with several methods and applications:
Haha. A funny thing happened to me last night. I wanted to dual boot my PC with Fedora workstation 38 and needed at least 15 GB of unallocated free space in the same drive. I had 137 GB of free space available, but when I tried to shrink the drive, it allowed me to shrink a maximum of 14 GB. So, I deleted some files and turned off some Windows features shown in a YouTube video tutorial. After installing the OS, I noticed my Windows files got corrupted, and I had to format the SSD without having any backup. My HDD was also damaged simultaneously with 1.5 TB of files, and now I got fu**d up. I found some bugs and difficulties on Fedora workstation 38, so I installed Debian 12 this time. I hope everything will be fine, and I guess it's my end with Windows! I am already having some difficulties with Linux as I am a new user.
I once experienced something like what you experienced when I was just learning computers (I remember using Windows 98). Because the hard disk capacity was starting to fill up, I deleted several Windows OS files, which turned out to be system files from the OS, and the result was that the OS became corrupt. However, I can learn from this experience.
Instead of using dual boot by dividing partitions, why don't you first try using a virtual machine such as a virtual box or others to test specific operating systems, including PGP Signature, on different OS?
I use MacOS as the primary OS. I run other OS using a virtual machine for testing PGP Signature or another application.