Our goal with Walling is to create a beautiful looking app with an intuitive experience to help you collect ideas and organize projects into visual boards/walls.
We've just released the Windows desktop app and that makes Walling available on the web, macOS, Windows, Chrome/Firefox extensions. iOS/Android apps are in the making!
I don't think Walling is competing with Notion. The two tools may look similar but they have different directions. Walling is more of visual boards to collect and organize ideas into bricks (blocks) and sections. You can also add tags to those bricks and be able to curate those bricks/ideas from different Walls using the tags filtering.
Notion pages are not visual boards and it doesn't for example has inline tags and many other current and future features that Walling has. It's not because Notion is missing those features but because Walling is focused on one direction and that is collecting and organizing things visually.