https://mozilla.github.io/geckoview/sandbox compatible? Elaborate pleasePWAs would be awesome, agreedbad for casual, non-techie users, which expect pages to workevery site that supports opensearch is supported, just go on a page supporting it, click on the address bar and click on the green plus symbolside bar exists as an API for extensions, same for containers! Mozilla provides an official extension: https://addons.mozilla.org/en-US/firefox/addon/side-view/