https://github.com/TrianguloY/UrlChecker
It also integrates ClearURLs functionality (https://gitlab.com/KevinRoebert/ClearUrls) to let you remove tracking from links before sending it to the browser or app. This feature is optional.
Previously,
1. you had the choice of activating the "tab queue" system for links opened with Firefox, i.e. the URLs would then only be saved in a list in the background instead of launching the full browser.
2. when sharing an URL with Firefox, you had the aforementioned choice of "actually open the link", "bookmark it", or "use Firefox Sync to send the URL to some other Firefox instance in your Sync account". The latter two choices happened in the background, so you didn't have to wait for the full browser UI+engine to start first, the page to load, etc. etc.
I use different browsers for different things so I want to chose how to open external app links.
I would install a shim browser that does just that if I knew of one.