It's look like project isn't actively maintained since spring 2019. There are bunch of issues and unresolved useful merge requests. Main maintainers don't work on this project.
It seems like only @alalamav fixing some issues from time to time (thank you for that!!!)
Outline Client:

Outline server:

@fortuna @trevj @alalamav @JonathanDCohen please, answer - what is the future of the Outline?
What is happening to Outline right now?
Thank you for your work and great project! 鉂わ笍
Outline is very much alive, we've just been focusing much more on the server. We are currently even onboarding a new engineer! What did happen there in early 2019 is that @trevj left the team and I joined and had to start onboarding, which left a large knowledge vacuum.
There has been a constant flow of changes to Outline, in this repository and the other ones. Some things we did since spring 2019:
Here are some of the announcements: https://www.reddit.com/r/outlinevpn/?f=flair_name%3A%22Announcement%22
Our team lost a few engineers, but we've re-staffed the team recently.
Outline is indeed alive!
Regarding work on the clients, I would add that last year we focused on migrating the clients' network stack to Go from shadowsocks-libev and badvpn-tun2socks. You can follow the progress in outline-go-tun2socks and alalama-go-tun2socks.
The Go network stack has been rolled to production for iOS and macOS, and is being beta-tested in other platforms. Those contributions are not in master yet, so I'm not sure if they appear on the repo contibutions graph.
Thank you very much! I'm glad to hear that.
@JonathanDCohen Why don't you update Outline?
The outline has many problems :(
https://github.com/Jigsaw-Code/outline-client/issues/781