Here is the mail from UEFA.
ŤUEFA has today announced that it has replaced two of the referees appointed for the UEFA Europa League match Molde vs Arsenal FC scheduled for Thursday 26 November at 18.55CET as one of the match officials appointed for this match has produced a positive covid test upon arrival in Norway and two officials have subsequently been placed into quarantine by local authorities. The referee (Irfan Peljto) and 1st assistant (Senad Ibrisimbegovic) from Bosnia remain as planned. The 2nd assistant referee will now be Dawid Igor Golis and the 4th official, Daniel Stefanski, both from Poland.ť