While I have modified Minecraft itself before, I have not used forge. I downloaded a bunch of different versions yesterday to try to get some combination that worked, and have failed.
I have seen the following comment by diesieben07 in another thread:
For this, I will set my path variable to jdk 8, despite updating my jdk yesterday. Path now = C:\Program Files\Java\jdk1.8.0_74\bin, among other things.
I have created a new and empty file at c:\[thepathtothislocation]\[username]\download\helpCenter
I have re-downloaded the recommended mdk found at this page https://files.minecraftforge.net/net/minecraftforge/forge/
The file forge-1.16.5-36.1.0-mdk (2).zip is now the only file in the helpCenter folder.
I have extracted the contents of the mdk zip into the helpCenter folder.
Now, as a proof of concept, as something that should be absurdly simple and easy, I open command prompt as administrator. I navigate command prompt to the folder 'help center' and I issue command 'gradlew build' without changing anything in the files I have just extracted directly from the mdk I just downloaded.
I have tried what feels to me like an absurd number of things to get around this most basic hurdle. When I enabled both TLSv1.2 and 1.3 I got an error that simply read 'TLSv1.3' with no more useful information, so I removed that line. When I attempted to download a certification through my browser and hopefully toss it in the right folder, that had no effect. When I ran the same command with the -info prefix it mentioned the following.
and when I navigated my browser to "https://repo.maven.apache.org/maven2/net/" I found that there was no "minecraftforge" folder. This resource legitimately does not exist. This is extra frustrating because there is no mention of 'maven2' anywhere in the build file, the properties file, or any other file I knew to check. I simply do not understand the keytool tool or gradlew itself well enough to even approach a solution or understand half the discourse I can find on the topics. I can't even be sure that cirtification is the real issue here. And no, changing the https to http and vice versa didn't seem to do anything, though I would be fine with going through the motions again.
I originally wanted to make a proof of concept for the simplest modification I could make, but at this point I'm just trying to get the program to run at all.