- Right click Garry’s Mod in your steam library and click properties
- Go to the betas tab and enter
iloveawesomiumin the password box (if the password doesn’t work move on to the next step)
- Select the
chromiumoption from the menu
- GMod should download an update now, once it’s done you should be good to go.
You might need to switch back to the standard branch if you want to play on a gamemode like Cinema or use the media player addon as this is pretty experimental and has been in beta for a very long time.