Yup, RetroArch for most things (GBA: rumble patch in Wario Land 4 and HD mode 7 in Car Battler Joe; SNES: widescreen Super Metroid Redux).
I installed Lakka for Saturn emulation, but the performance isn’t great and you have to use attached original joycons and handheld mode rather than docked.
Edit: Injection into Cotton/Guardian Force works much better, and allows docked play and third-party controllers. But there's no upscaling option. This is fine for 2D games like Saturn Bomberman, and not too bad in 3D for Panzer Dragoon Saga as I can set the Switch's output to 480p and get my mClassic to do most of the upscaling. It's closer to what I would have seen on a real Saturn, and the FMW cutscenes and sound aren't broken the way they were on previous upscaled playthroughs on Yabause on computer.