I wonder why it's not permitted to have multiple instances of an application with different configurations.
It's an alternative to Island, except it doesn't have analytics (Insular is a fork of Island w/o that, but Shelter is a newer and better app imo)
(This a biased personal opinion not based on a real experience)
Judging from thr screenshots it is the same framework used by many Android apps (most notably for me by Nextcloud) and it is really sucks.
The current FastMail app is sadly dependent on gapps (AFAIR FireBase dependency) but othereise it is just an SPA in the guise of an Android app which works marvelous... till you have the connectivity.
If you need an offline access to your mail then the FastMail app isn't for you.
https://play.google.com/store/apps/details?id=com.fastmail.a...
Really curious in what world that can be considered native.
I use the Fastmail Android app and didn't realize it's just a webview.