For anyone who wonders how I solved my issue:

I created the file ~/.config/systemd/user/protonmail-bridge.service and wrote the following into it:

[Unit]
Description=ProtonMail Bridge Flatpak Service

[Service]
ExecStart=/usr/bin/flatpak run ch.protonmail.protonmail-bridge --no-window
Restart=always
RestartSec=10

[Install]
WantedBy=default.target

If you are not using the Flatpack version of ProtonMail Bridge, then modify the ExecStart value to your installation.

After that I ran systemctl --user start protonmail-bridge.service to start the service and systemctl --user enable protonmail-bridge.service to make it auto-start upon login-in into my account.

This did it, tanks!

Launching the App at startup is not my problem (at least not for now). It is rather that I would like to have ProtonMail Bridge minimize into the background applications list (like steam does, shown in the screenshot appended).

It seems, that I cannot answer from mastodon, therefore i will do it from lemmy.

Launching the App at startup is not my problem (at least not for now). It is rather that I would like to have ProtonMail Bridge minimize into the background applications list (like steam does, shown in the screenshot appended).