I changed the Slack.deb control file to Depend on libappindicator3-1 | libayatana-appindicator3-1 ( >= 0.5.90-6). That allowed it to be installed, but if 0.5.90-6 adds compatilibity for libappindicator3-1. maybe 0.5.90-7 can Provide it instead of Replacing it? Thanks, Gerardo