Under Windows, the 5 machine activations per 24 hours limit they impose wasn’t something I ever hit, but under Linux it’s kind of easy because, as the article states, switching Proton versions counts as a machine activation to Denuvo.

That limit isn't mandatory with Denuvo and Doom apparently doesn't have it. On Steam some games mention a limit on the store page, like Atomfall, Atomic Heart or a few Assassin's Creed games.

The Dark Ages EULA does mention something like Denuvo "may" limit installations, but then never says anything else.