I am self-hosting a Firefox add-on that users can download from my website. When a user clicks to download my Firefox add-on, Firefox displays a warning:
Firefox prevented this site (example.com) from asking you to install
software on your computer.

Is there a way to prevent the warning from displaying?
That popup is there for a reason, it protects users from getting potentially malicious addons without noticing.
Disabling it on your side is not possible afaik.