The new upcoming Serious Sam 4 game is now available to buy on Good Old Games (GOG). That also means that the new game probably will not get any DRM like Denuvo etc.
With GOG you are able to download the game files directly from any game on the store and install them on your PC without creating an extra account or install a launcher. You can use their GOG launcher, but it’s not needed.
Currently only the old classic Serious Sam games are on GOG, but the release of the new game on GOG probably could be a possibility that Serious Sam 3 may also get released on GOG. The new game is coming out on September 24.