Please check https://mark.show/
You can:
Write markdown in editor
or
Upload a markdown file
or
Import direct from URL of markdown file.
PS: I am creator of the service.
You can:
Write markdown in editor
or
Upload a markdown file
or
Import direct from URL of markdown file.
PS: I am creator of the service.
Apart from that, I find what really stops me from using such tools is the lack of control over the layout of slides. Just saying use CSS isn't really enough for me! I found gitpitch to offer pretty good layout options, but the service is too commercial for my taste.