In a similar vein to deadcade's comment, Ripcord also exists also an alternative. If this exchange had happened a few months ago I would've recommended it above anything - but unfortunately it hasn't been updated in a very long time at this point and it's starting to cause some core functionality to not work.
EDIT: It's pretty much exclusively the Slack functionality that doesn't work anymore. The Discord side is great and is IMO has a much more useful UI, ex: you can group arbitrary channels from any number of servers into a single group which is presented in the UI pretty much as a new server. No more server hopping to check out all of your favorite channels!
In a similar vein to deadcade's comment, Ripcord also exists also an alternative. If this exchange had happened a few months ago I would've recommended it above anything - but unfortunately it hasn't been updated in a very long time at this point and it's starting to cause some core functionality to not work.
EDIT: It's pretty much exclusively the Slack functionality that doesn't work anymore. The Discord side is great and is IMO has a much more useful UI, ex: you can group arbitrary channels from any number of servers into a single group which is presented in the UI pretty much as a new server. No more server hopping to check out all of your favorite channels!