The console detects the connection but fails to display any image.
According to GoNintendo, users across forums and social media are reporting en masse that third‑party docks stopped working after installing update 21.0.0. The Switch 2 recognizes the connection but does not send video to a TV or monitor. The official dock supplied with the console, however, continues to function normally.
Brands cited among those affected include GuileKit, JSAUX (certain models), Hagibis, and others. Some JSAUX adapters, the dbrand KillSwitch 2, and the VITURE Pro Mobile Dock still appear to be working.
Several manufacturers have acknowledged the problem and are working on firmware updates for their devices to work around the restriction.
Source: iXBT.games