Looks like a Switch firmware update is going to be dropping very soon. This is confirmed by Nintendo themselves, who make mention of the update on the official store page for the SNES Switch controller. The listing for the controller includes this blurb underneath.
A system update (9.0 NUP) is required in order to use Super Nintendo Entertainment System Controllers with your Nintendo Switch console.
When the Version 9.0 firmware update becomes available, we'll be sure to let you know.