There is #Ayatana Indicators, which seems to be the successor of #libappindicator. The last release of libappindicator dates 2020, whereas the latest #libayatana-appindicator dates February 2023.

And: #Linux #Mint and #Ubuntu (#GNOME) come with #libayatana-appindicator installed.

https://github.com/AyatanaIndicators

#Ayatana #Indicators has just received a pull request on Github by Robert Tari that will make indicators finally available to all Linux systems running vanilla Gtk. Up to now, the full functionality scope (rendering of custom widgets via GMenu) was only available in Ubuntu. This is an a hell of a milestone. Sending out my biggest gratitude to Robert, before I have even tested his PR. light+love from sunweaver