Do you use the Curseforge launcher to make custom Minecraft modpacks, but despair that you can't use them on Linux? Or just want to switch to MultiMC? This post will detail how you can use packs you made, in MultiMC.
First, we need the pack folder.
Get this folder onto your Linux installation, either with a USB, the cloud, or somehow else.
Open MultiMC on Linux (if you don't have it, get it at https://multimc.org/).
Create a new instance:
and select Vanilla with the right Minecraft version.
In MultiMC, select your new instance, and open the folder by selecting "Minecraft Folder" in the panel to the right.
In this folder, delete the existing ".minecraft" folder (if you can't see it, you may need to turn on "Show hidden files" or similar in your file manager).
Then, replace the ".minecraft" folder with the previous folder we obtained in step 1. Make sure that the name matches exactly.
In MultiMC, click "Edit Instance" in the same panel you found "Minecraft Folder". Click onto the Version tab:
and click on the install button for your desired modloader.
If you want, check that the right mods were installed by clicking "View Mods" in the panel to the right.
If that's all good, launch the new instance just like you would launch one normally! If it crashes with a message saying that 1.17+ requires Java 17, simply click "Settings" in "Edit Instance", and change your Java installation to the right one.
Hope this helped!