How to use your mobile web browser to access your Steam friend's list and chat with Steam friends
This video will show you how to access your Steam friends list, how to see who is online, and how to chat with those on your Steam friend's list using a web browser on your mobile device. In this video I use the Microsoft Edge web browser on Apple iPhone, but I can confirm that this method also functions in the Safari web browser, and it is presumed that this method will also function on a modern Android device.
Open your mobile web browser and go to:
steamcommunity.com/chat
Once on the site, login with your Steam credentials. If, after logging in, you are not brought to your Steam friends list, once logged in, again go to:
steamcommunity.com/chat
You should now have access to your Steam friends list, where you can see which of your Steam friends are online and subsequently type to them within your mobile web browser. Keep in mind that if the chat window and text entry field are too small to see well, then at the top of the page you have two chevrons (arrows) pointing left - tap on these to collapse the friends list, leaving the active chat window maximized in the forefront.