The default templates of Incoming and Outgoing messages are not working in my version.
When downloading your example from github, it works.
When I copy and paste your code to my project ( copying 100% the same), it's like the "CurrentUser" is not being reconized and also the Avatar property (images never appear). So, what happens is that all the Messages appear like incoming messages.
I am using SfChat 20.3.0.48 , but also tried with the 20.3.0.49 and Xamarin.Forms 5.0.0.2196 and it's not working.