This doesn't seem to work for me on a Windows 2019 Server. I edited and re-hosted patches.json on an https server and get errors when running, although I can download any patch via the browser on that same server.
c:\Program Files\ArcGIS\Portal\tools\patchnotification>patchnotification.bat -c -u https://rehosted-endpoint.cloudfront.net/patches.json -i all
================================================================================
ArcGIS Enterprise Patch Notification
================================================================================
Collecting patch info for:
Portal for ArcGIS 10.9.1.....
-------------------------------------------------------------------
Installing: Portal for ArcGIS Log4j Patch
<<<<
Error downloading patch file:
Patch File Download Exception: Error connecting to remote host. Did you check your proxy settings?
>>>>
Status: ERROR...
-------------------------------------------------------------------
...
If I search for that patch name in patches.json and paste the link to the msp into the browser on that same server, it works fine.