To support the developers (Gears for Breakfast) and ensure you have access to the Steam Workshop (which is a huge part of the game's longevity), purchasing the game on Steam or GOG is the recommended way to play.
: Repacks can take a long time to install because your computer has to decompress the files. If you have a slow CPU, a "clean" steam rip or a GOG version might be a better choice.
: This "Ultimate Edition" build typically includes the base game plus major DLCs like Seal the Deal and Nyakuza Metro .