Viking depends in where you are. In my country, Norway, viking iconography is a pink flag. Yeah we have dipshit Nazis who use it, but it's fairly main stream. Viking rock is a little sus, but not necessarily as sus as elsewhere.
I meant as in red flag lite, but I see the ambiguity. The viking reenactors are just regular and LGBTQ+ is usually not an issue I'm Norway so guess they have their fair share of all the colors of Heimdall rainbow. The Viking metal I don't know, as metal go in Norway it's not a huge thing, but I am no metal fan tho'