My issue was that even after I downloaded slack, and I did:
cd ~/Downloads dpkg -i slack-desktop-2.6.3-amd64.deb
I got errors about missing
So I do the next logical thing right?
sudo apt-get install libappindicator1, this too resulted in an error. Oh well, jeez I though, I know this is beta, but really? I can't even install it with one command?
How to resolve this? Read my one line answer below.