McAllister had posted a picture from Lisbon on Facebook just hours before the match. He was fondly known as Tam to friends and was a resident of Drumchapel in north-west Glasgow.
Rangers CEO James Bisgrove said: "On behalf of the club, I want to pass on my sincere condolences to Thomas' loved ones, family and his friends.
"This news has hit everyone at the club extremely hard, as I am sure it will all of our supporters. Nobody should ever go to a football match and not return home. The club stands ready to assist Thomas' family in whichever way we can in the coming days and weeks."