Syncing iCloud bookmarks with Opera GX?
If you create the NativeMessagingHosts registry entry it syncs fine without Chrome being detected.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Google\Chrome\NativeMessagingHosts\com.apple.bookmarks]
@="C:\\Program Files (x86)\\Common Files\\Apple\\Internet Services\\AppleChromeDAV_host_manifest.json"


In the UWP version of iCloud both Firefox and Chrome keys are already exposed by the AppX though you can't see them in the registry. So any browser should just work if you install the iCloud extension.