Comment 29 for bug 1967632

This seems similar: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_messaging
IIUC Firefox and Chrome (as important as systemd) need to be able to start binaries that are defined in certain json files. Those binaries are installed by non-snap packages or scripts and need to run as the regular user. Such a binary can be used to control other applications or to talk to hardware or to flash firmware.

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests
> There are three different types of native manifest:
> * Native messaging manifests
> * Managed storage manifests
> * PKCS #11 manifests

> Linux
> For global visibility, store the manifest in either:
> /usr/lib/mozilla/native-messaging-hosts/<name>.json
> /usr/lib/mozilla/managed-storage/<name>.json
> /usr/lib/mozilla/pkcs11-modules/<name>.json
or:
> /usr/lib64/mozilla/native-messaging-hosts/<name>.json
> /usr/lib64/mozilla/managed-storage/<name>.json
> /usr/lib64/mozilla/pkcs11-modules/<name>.json
>
> For per-user visibility, store the manifest in:
> ~/.mozilla/native-messaging-hosts/<name>.json
> ~/.mozilla/managed-storage/<name>.json
> ~/.mozilla/pkcs11-modules/<name>.json