During the announcement of the MacBook Pro M3, it was known that the laptop couldn’t connect to two external displays. This was despite the fact that a similar capability is available on the MacBook Air M3.
In macOS 14.6, the issue has finally been resolved. The release notes state that the MB Pro M3 now supports up to two external monitors.
However, there’s a catch. Multiple monitors can only be used when the MacBook’s lid is closed. [9to5]