OK if you go to Discord.com and click on the “Open Discord” button you can use discord totally in the browser
from there I’m not 100% sure how you proceed as you should already have a log in from the desktop app (I think)
but I suspect you will need to add a server (click the big green + in the left hand side)
and then you get a couple panes to add a new server (you dont want to create one)
and the invite link from the beginning of this thread should work (I think)
I’m guessing on a lot of this though