Nintendo released firmware update 4.0.1 for the Nintendo Switch yesterday. This update, according to the official changelog, brings “General system stability improvements to enhance the user’s experience”.
In particular, this firmware update seems to fix HDMI issues with some TV models.
There’s no indication that Nintendo Switch 4.0.1 fixes any undisclosed exploit from the scene. Currently, the scene is waiting for some progress on ROhan, the upcoming exploit for 3.0.0.
There is no publicly known (let alone released) hack for firmwares 3.0.1 and above. That being said, even if you are on a higher firmware, it is recommended to stay on as low a firmware as you possibly can if you have expectations to hack your console ultimately.
That is, unless you are one of the people expecting to fix their HDMI issues.