On Fedora 38/Gnome 44. There is no tray icon using latest version of Slack.
If I install previous version with sudo flatpak update --commit=b95d24a8a354db07b95b065b3e57e9442c9fbaf851a49cbe6e7b1aa0afcab591 com.slack.Slack there is a tray icon.
For viewing tray icons I use "AppIndicator and KStatusNotifierItem Support".
On Fedora 38/Gnome 44. There is no tray icon using latest version of Slack.
If I install previous version with
sudo flatpak update --commit=b95d24a8a354db07b95b065b3e57e9442c9fbaf851a49cbe6e7b1aa0afcab591 com.slack.Slack
there is a tray icon.For viewing tray icons I use "AppIndicator and KStatusNotifierItem Support".