Valve are now testing a new version of the Steam app for Android and iOS, which comes with a much more modern design and a QR code login system too.
From the announcement Valve say it has been rebuilt "on a new framework and modernized the design", joking that 2015 called and wanted their app back. As before you can browse the store, get Steam Guard codes and confirm trades but you also now get the brand new QR code sign in system that many other applications also offer (like Discord). So you can scan it with your phone on the web, and not have to enter a password.
The new app also has smarter notifications, an improved library views and there's also now multi-account support which has become increasingly important especially with the Steam Deck now too. There's a new Steam Group you can join to get updates on it.
I would have taken some shots, but seeing as I'm now on iOS myself it's limited to 10,000 people and that filled up within seconds of the original announcements. Here's some shots from a reader on Android (click to enlarge):