Does MC runs on gentoo distri ?
It might work on Gentoo, but since Media Center only officially supports Debian, your results may vary and it's something you'd have to figure out yourself.
Is the installation process the same as the rpi4 installation ?
No it's not. The Raspberry Pi's OS (formerly known as Raspbian) uses APT with .deb packages. Gentoo does not use this, so it's different.
