According to GoNintendo, users on forums and social networks are massively complaining that their third-party docks have stopped working after installing update 21.0.0: Switch 2 recognizes the connection, but does not display an image on a TV or monitor. At the same time, the included docking station works without problems.
Problem brands include GuileKit, JSAUX (some models), Hagibis, and others. JSAUX and dbrand KillSwitch 2 and VITURE Pro Mobile Dock adapters continue to work.
Some manufacturers have already confirmed the malfunction and are working on updates for their devices to bypass the blocking.