Debian-based distributions (Debian, Linux Mint, Ubuntu, elementary OS, ...) cncnet_1.0_all.deb
RPM-based Linux distributions (Fedora, openSUSE, ...) cncnet-1.0-2.noarch.rpm
Pacman-based Linux distributions (Arch, Manjaro, Antergos, ...) cncnet-1.0-1-any.pkg.tar.xz
You can also try PlayOnLinux
Full game via CnCNet app CnCNet.dmg
Full game via Porting Kit: Porting kit
Alternative ways to install the game (complicated, only use PlayOnMac if the above downloads are not working)
Click "Install a non-listed program" at the bottom
Choose "install a program in a new virtual drive"
Click browse, choose RA1installer.exe and install the game
Enjoy the game!