I'll have to look into this, if I buy Legends digital on Switch 1, if I do get Switch 2, can I reload and use same SD card so I don't lose progress?
As long as it works like all the other “switch 2 editions”, yes, this should work. You won’t use the “same” SD card necessarily, but when you set up switch 2 it asks you to insert your switch 1 SD card so it can transfer over all the save data.
I know everyone here has moved on long ago, but I’m finally getting around to completing the Pokédex from my original save file for Shield. Down to the last 10 or so. Not sure yet if I want to continue with the DLC or just buy one of the newer releases.