There are a bunch of bars in Gamla Stan, such as O'Learys, O’Connell’s Irish Pub, The Liffey etc. and all of them will be showing the game.
Not in Gamla Stan, but if the weather is good (meaning not raining), the outdoor bar "Gården" located on Norra Bantorget, will be displaying the game on large screens. Opens 13:00, you will want to be there early if you are hoping to snag seats.
*Edit: Tickets for Tele2 Arena seem to be almost sold out. Only tickets for section B remain. Section B does not give one access to the field with the bars selling snacks and drinks but rather only a seat on the stands.Edited: 05 July 2018, 23:01
Thanks a million, really helpful