Well, he tried to install newer versions but got stuck everytime : /
I checked all my folders with mods in it and I think I've got just one copy
This folder was here when I installed the game, I didn't create it. So I don't know why you don't have it. For me it's in my VintagestoryData folder.
That's interesting, I'll check that, thx
Edit
Another problem is that in my server-main.txt, it's not the good server which is shown I think ^^'
And also, I found that on the wiki :
"Starting from Vintage Story 1.16, when you connect to a multiplayer server which offers a modded game, it will automatically set up the mods correctly for that server on the player's side. It creates a folder(names it on its own by IP or servername) in ModsByServer folder for each different multiplayer servers it's located AppData\Roaming\VintagestoryData\ModsByServer"