My installation is not messed up.
Yes it is. Or, at least it was, you said that yourself:
I had 2 “community” folders
I can only comment based on what you said and, clearly, no proper MSFS installation should have 2 community folders.
What happens is that after installing MSFS2020 it allows you, through the settings, to change the simulator cache folder and with that it also changes the location of the “Community” folder through itself, where you designate a new folder and it naturally migrates all for her. So much so that my other Addons like PMDG work perfectly beyond scenarios. In summary, I didn't move or copy anything manually, it was done directly by the simulator.
Sure, you would guess I *know* how the MSFS installer works...but you can be sure it doesn't create 2 community folders.
About the “solution” I found, I didn't move any folders manually. What I did was create a shortcut/link from the shortcut/link created by GSX during the installation and this new shortcut/link I threw in the “community” folder that I found duplicated. I emphasize that this folder also had PMDG files (different files in the 2 “Community” folders) and FSUIPC
I'm not sure I follow you but, in general, you shouldn't create a "link to a link", even if *might* work, it will be very confusing.
This second folder was created by MSFS2020, what is the risk of causing damage to the simulator and/or other add-ons?
No, it wasn't. When you uninstall the sim, sometimes it leaves an EMPTY "Packages" folder, but what matters is what is being pointed in the UserCfg.opt file, an eventual leftover folder won't affect it, if it's not referenced by the sim.
This UserCFG.opt file is a GSX or MSFS2020 file, because if it's from the simulator, the file is correct. If it's from the GSX I can change the location to the correct folder
The UserCfg.opt file is NOT a GSX file. If the one and only file that stores the location of the CONTENT folder ( which contains Official and Community ), and GSX *reads* that file (it never writes to it or changes it ) to know where the Community is. MSFS ALSO use that file to set its content.
The issue, which I explained in the thread I linked, is that some tutorials suggests to move JUST the Community folder and "link it", which is wrong on so many levels, both because it miss the chance to save lots of space, because it only moves the Community folder and not the 180GB+ in the Official folder, but also because the proper way is the one the MSFS installer does, which GSX obviously respects, and it's moving the complete "content" folder (that one that *contains* Official and Community), and point to it in the UserCfg.opt file.
The post I linked, does manually exactly the same thing the MSFS installer does when it ask you a different location for the content, so it's useful to CONVERT a bad installation ( Official and Community in two different places, with Community linked), into a proper one. I don't know if that was your case, but understanding that explanation is useful anyway.
I think it would be best if I could designate the folder where the links should be made by GSX, as it installed in the correct Community folder, but it cannot read it, which is strange considering that PMDG, for example, installed it the same way and it works correctly.
Please clarify, because this doesn't make much sense:
"it installed in the correct Community folder, but it cannot read it"
If it installed in the correct Community folder, it means GSX *COULD* read it. Or, where you trying to say GSX could read it and installed into the correct Community folder, but the SIM couldn't see GSX, so you had to copy manually ?
I'll take a look at the link you sent me, but can I change the folder where the links will be made?
Please re-read that linked post carefully, because it explains how a proper installation should be.