Not sure if this is the right place to report site problems, but here we go anyway:
On the site, click Download, and one of the options is a command for winget:
winget install 'Flow Launcher'
Powershell doesn't seem to understand the apostrophes:
No package found matching input criteria.
Package not found: 'Flow
No package found matching input criteria.
Package not found: Launcher'
Changing them to regular quotes worked.