An alternative (which doesnt fully meet your requirements for browser based) is Jetbrains Rider. You can use its remote development feature to have your code on your server, and the IDE on your local computer.
Another option to get code to and from your device would be to use git to commit and push your code. There are git apps for android that should work for this?
Self hosted browser IDE that supports C# and runs on Windows
My server is still windows based, which I know is a bit of a sin at this point, but just bear with me please...