Currently CurseForge app works only for Win/Mac and Linux will be added later on. It's okay. But modpack it's just a list of mods and some overrides so it can easily be configured to play from a regular minecraft launcher.
Right now I'm using a workaround like asking a friend to zip me installed modpack; or installing Windows on a virtual machine and then copy paste parsed by CurseForge app modpack and installing overrides manually. I prepare a proper Forge version through the official minecraft launcher and then just copy what I prepared before.
It's inconvenient! I know that there's a modlist.html where all the mod links lie but you can't download it with script (keep getting 403). Just allow some way for Linux users to apply modpacks not through the CurseForge app, at least temporarily till Linux support is added.