Central attacking midfield, or if you like, the position Szmodics plays. Markanday will also be behind Sigurdsson for that position. But just to clarify, it would help if players were played in their best positions.
And still the answer is, I don't know. But I did not know last season ,or the season before, or the season before that. If I had to take a guess I would say Sigurdsson or Markanday.
Sigurdsson ! Szmodics is an attacking midfielder not a striker The ones you have mentioned are strikers of varying ability . They do not play in Szmodics's position.