FYI there is probably a better way to run league on your steamdeck
I am by no means a super technical person, but it's a fact that the instructions provided in the page about how to install league on my steamdeck did not work no matter how hard I tried.
What worked for me was essentially:
Install lutris flatpak
Download GE's lol-wine version
Manually download the league installer from rito's site
Manually invoke the downloaded wine executable to run the installer