Updated Install on Linux (markdown)

Install-on-Linux.md

@@ -4,6 +4,12 @@ SNAP package steps:
 2. Then open a Terminal in the folder that is the downloaded file.
 3. Type: `snap install --dangerous Rambox-0.7.3-linux-amd64.snap` (replace Rambox-0.7.3-linux-amd64.snap with the name of the downloaded file).
 
+Debian package steps (including Ubuntu, Linux Mint)
+
+1. Go to [the releases page](https://github.com/ramboxapp/community-edition/releases) and download the latest `.deb` file (`amd64` for 64-bit systems; `i386` for 32-bit systems).
+2. Open the file with your system's Package Manager or Software Manager.
+3. Follow your system's prompts to install.
+
 Zip package steps:
 
 1. Go to https://github.com/ramboxapp/community-edition/releases and download zip file for Linux.