On Phiewer.com you can download always the lastest version before it gets approved by the AppStore.
The versions on Phiewer.com are un-sandboxed. This means there are no restrictions for accessing folders. So you can open Phiewer without clicking on the extra “Allow to access folder” dialog.
The direct download comes as a typically .dmg image from where you can drag the Phiewer app directly to your applications.
Phiewer – Mac os image viewer