Signal is one of my favourite way to communicate remotely with friends: its cryptography is top-notch, its privacy policy is one of the best, its applications useable by all, … there is even a desktop client which feels clunky but at least it's something.

It's possible since 2017 to minimize Signal Desktop to the systray, but this isn't exposed in the options because the feature is still in beta: the trick is simply to pass --use-tray-icon to the binary. And while you're at it, you can remove the --no-sandbox from your desktop shortcut.