They don’t have to make a Linux version. Wine is a program that allows you to run windows programs on Linux. The reason it doesn’t work with fortnite is because fortnite anticheat blocks it. In order to let Linux users (including steam decks) play fortnite, they just have to change an anticheat setting not to block Wine. Fortnite uses battleye and eac, both of which have wine support
I genuinely don’t know the last time I used the activities button, or the taskbar. To open activity view, I press super. To open programs, I search. To switch programs, I click on them in activity view