Installing a .deb package on Arch - Is it possible?

Is it possible? Yes. Is it a good idea? That depends. You would only really need to do this if the application only exists as a .deb package. It is much more likely that you can just grab the upstream source and write a simple PKGBUILD to install it with pacman.

You should also search the AUR to ensure that someone hasn't done this already.

dpkg for Arch exists. You should be able to install .deb packages on arch, but you should also not use it instead of pacman, so just use it for selected few packages.

The default command looks like:

# dpkg -i package.deb

Possible? Yes, but different methods exist on basis of use case.

Assumption: The debian package doesn't have an equivalent package in the Arch (or Arch based Distribution's) official repository.

1. Install yay using pacman:

    sudo pacman -S yay
   

Reason: yay is an AUR helper used to query & install AUR packages. In case the debian package has already been repackaged and published to the AUR by someone else.

2. Install the package_name using yay:

    yay -S package_name
   

note: replace package_name with the name of the debian package as found in the AUR. It'll attempt to install the dependencies on it's own using pacman.

Alternative

Assumption: The Debian package hasn't been repackaged as an Arch package in AUR yet.

1. Install debtap from AUR using yay:

    yay -S debtap
   

2. Create equivalent package using debtap:

    sudo debtap -u package_name.deb
   

3. Install using pacman:

    sudo pacman -U package_name.pkg
   

Not the recommended way (possibly dangerous)

This method attempts to install the package using the debian packaging format on Arch, which is not recommended due to possible danger of corrupting your installation. If using this method it is recommended to be ready with a rescue disc image of Arch & backup of the user data/space.

1. Install dpkg using yay:

    yay -S dpkg
   

2. Install the debian package using dpkg:

    sudo dpkg -i package_name.deb