Ah, Handoko, the truth is that Mate is one of the better ones in this space, for real trouble, try Gnome (can be made to work is you install gnome-shell-extension-appindicator and enable gnome-extensions). I too use Mate (I think I might have suggested it to you ?) and a quite old Ubuntu, it works in both modes.
Here is the list I tested today, the really surprising ones is the difference between 32bit and 64bit Debian Mate, with 32bit, must use old traditional System Tray, with 64bit either will work.
Its the erratic nature of these things, changes with each release, that convinced me that allowing the programmer to manage the situation was the only way forward.Bad with App Indicator only ie OK with Traditional
- 32bit Bookworm and Bullseye - both fail in AppIndicator mode, either 1 or 3
- Bookworm KDE - has no AppIndicator by default, AV
- Trixie KDE -has no AppIndicator by default, AV
Bad with Traditional SysTray only ie OK with App Indicator
- Ubuntu 2304 Gnome (in Traditional, menu pops up in random places)
- Ubuntu 2310 Gnome, as above
Good with either works with both App Indicator and Traditional
- Ubuntu 2004 Mate
- Bookworm Cinnamon
- Bookworm LXDE
- Bookworm Mate
- Bullseye Mate
- Trixie Mate
- Mint 21.1 Cinnamon
- Ubuntu2304 XFCe
- Ubuntu 2204 Mate
Bad with Either #@1 Gnome
- Bookworm Gnome (but can be made work)
- OpenBox, no (default) System Tray.
- Fedora Gnome
(Gnome generally fixable for App Indicator by installing gnome-shell-extension-appindicator and enabling it in in gnome-extension-app but traditional sys tray is still non-functional as menu appears in random locations.)
By Traditional, I mean hitting the DE's api, by using an App Indicator, we bypass the DE, directly open the library and use it's calls to do what we must. Most of the "works with either" ones also rely on LibAyatana and connect their API to that Library.
KDE implements its own solution.
Davo