I generally avoid Steam games with third-party DRM due to issues the legacy copy protection schemes in particular can cause (see a question on Super User).
Resident Evil 7's Steam page as an example:
I'm fairly sure that the support is either inadequate or up to the developers (who may leave the DRM note out on purpose) as I have encountered Steam games that have some third-party protection according to PC Gaming Wiki and/or ProtectionID program (PC game "protection scanner") and no mention on the game's store page.