Unpacking .7z files tutorial - Bannerlord Software Extender (BLSE) mod for Mount & Blade II: Bannerlord
The first step to opening a non-zip mod is installing software on your computer that can open it. On Windows, you can use a program such as 7-Zip, which is free and open source, meaning you can check the code yourself and modify it before installing...
Source: moddb.com