I feel like this should be mentioned, so I'm adding it on.
With the release of Gen 8, we have added a new system of TMs, Galarian TMs and TRs. Pokemon that can be transferred to Sword and Shield like Togekiss can only use Galarian TMs or TRs, they can not use the old TMs. Any pokemon that returned with the Isle of Armor DLC have their TM list borked and currently do not have a TM list, this issue is fixed next version and can be seen here:
https://pixelmonmod.com/tracker.php?p=2&t=15133. Pokemon that returned with Crown Tundra or Pokemon that currently can not be transferred to Sw/Sh are still using the Gen 7 moveset and still use the old TMs.