How do you define "commercial software"? Spotify, Zoom, Steam, Discord, Postman, IDEA Ultimate, and lots of other end-user software that is built by companies and where people pay for things (i.e. commercial software?) is available through Flathub.

Most commercial software in general can be downloaded as a free demo version and then activated with a license key or account, and that model works really well with Flatpak and even Flathub.