And sadly all android webviews are Chrome (and with a lot of additional effort at least Chromium based). Mozilla should release a webview and fight for signature inclusion.
I'm not an Android expert but when I click a link in an email it opens the preview via Firefox (I've set it as the default browser). Is it another thing?
That's a feature called Custom Tabs. It's essentially a small barebones Firefox app and yes it is using Gecko.
The parent poster is talking about system webviews. They're used when any app wants to show web content embedded inside their apps, and yeah there's no Firefox option for those.
Android allows for Gecko web views (1) and Firefox Custom Tabs. It’s just that the Chrome Webview is available by default and does not need to be embedded, thus reducing app size and load times.
Not strictly related to the current thread but I used apps (now uninstalled for that specific reason) that insisted on trying to open Chrome's Custom Tabs and just crashed if that wasn't possible; never found a way to redirect those that didn't require rooting.
LinkSheet [1] can do that. It's a small app that you set as the default browser and shows a prompt when you open a link to allow you to choose what to do (eg. open in browser, open in app, share link, remove tracking URL parameters, etc.).
If you don't care about any of the extra functionality, you can configure it to always open your preferred browser and convert Custom Tabs intents to regular ones. No root access required.
