Inspecting RPM/DEB packages
An RPM package (.rpm) is a package which is used to store files/scripts/conf files on RedHat systems.
Likewise, .deb files (Debian/binary packages) contain similar contents for Debian-based systems.
$ file protonvpn-stable-release_1.0.0-1_all.deb
protonvpn-stable-release_1.0.0-1_all.deb: Debian binary package (format 2.0), with control.tar.xz, data compression xz
To unpack .deb files, you can either use dpkg -c like so;
$ dpkg -c protonvpn-stable-release_1.0.0-1_all.deb
Or you can simply use tar -x, like so;
$ tar -x protonvpn-stable-release_1.0.0-1_all.deb
Or use dpkg-deb;
$ dpkg-deb -x protonvpn-stable-release_1.0.0-1_all.deb .
This will create the files/directories which would be modified/created if you were to install the package with dpkg.
RPM - TBA