This idea has been merged into another idea. To comment or vote on this idea, please visit CF-I-42 Linux Support.
The launcher already supports Windows and macOS. Additionally, Forge already works since Linux has the open-source implementation of Java (openJDK). The only thing missing then is the UI, which hopefully wouldn't be too difficult, given that it is a wrapper around Forge itself. Thanks for looking at this (if you do)!