If you have long-abandoned Miis from the 3DS days, there's a complicated way to transfer them to Tomodachi Life: Living the Dream — here's how to do it
A way to transfer Miis from 3DS to Tomodachi Life: Living the Dream on Switch and Switch 2 has been found, but the process is a little complicated.

Source: TechRadar
A way to transfer Miis from 3DS to Tomodachi Life: Living the Dream on Switch and Switch 2 has been found, but the process is a little complicated.