It seems that the new patch for the Switch version of Skyrim Anniversary Edition has fixed the framerate issues. The latest patch (version 184.108.40.20685177) is quite cumbersome, but it brings something very useful. Many players have complained in the past that the game on Nintendo Switch had a rather nasty frame rate issue. In some areas, the frame rate sometimes dropped to 15-20 fps.
A new YouTube video from Xiphos Gaming made a side-by-side comparison of the game running before and after the patch. It turned out that the Anniversary Edition after the patch now runs at 30 frames per second. This applies to various areas such as Falkreath, Morfall and Solitude. The update also fixed various game crashes.