It does seem there were some scenes cut from the film; from the ‘The Rise of Skywalker The Visual Dictionary’ (out on the 22nd December - though seems some have been sent out early), in this case Kylo Ren and ‘Cult Colonists’ on Mustafar:-
That guy looks like the ones Kylo fights in the first scene, which presumably takes place on Mustafar.
Ha! I’d completely forgot about that scene - doh! Thanks, man. I’m definitely going to have to go and watch this again 😃