you can go with Mac AppStore version of Slack else you need to change the update settings in config file or plist file in Library folder. Will try in some time and share if you want.

Sadly we switched off from the AppStore Version since it wasn’t updating correctly.
Lmk if you find out anything about that!
Thank you

You can use these key, 

<key>SlackNoAutoUpdates</key>

<true/>

or 

<key>SlackNoAutoUpdates</key>

<true/>

more info check out in https://slack.com/intl/en-in/help/articles/11906214948755-Manage-desktop-app-configurations#h_01GV192YCK2P7VG9JWG5W7ARE5 

I use AppStore version app by creating pkg from it then distribute with policy, also add the app in VPP and disable the auto update in it. when ever required will repackage and re distribute, with this i’m not faced auto update issue for Slack untill people login to AppStore on their Mac.

 

for some reason my replied it getting deleted