Fact: even after the disastrous life of the Wii-U, Miis still exist on the Nintendo Switch, and even though a lot less fuss is made about them now, there are still games that support them.
There are also games that used to support them but no longer do. The version of Super Mario Galaxy on Super Mario 3D All-Stars doesn’t let you select a system Mii to use as the file icon. You’re limited to one of the Mario characters provided! It’s a shame that. But, Nintendo Switch Sports, Smash Ultimate, and of course Miitopia supports them, as do four other games on the platform.
I’ve actually been through the process explained in the below video, by CJCat, which involves using Amiibo to transfer Miis over one by one from a Wii-U that had a Mii collection brought over using the Wii import channel. We played a lot of Wii, and it’s nice to know all the goofy characters we made, and the memories they carry, are on the Switch, even if few games use them any more. I hope the Switch 2 doesn’t forget about them, and that it makes them easier to bring over!
Bringing a Mii from Wii to Switch (Youtube, 9 minutes)