debugManifestsFile property not accepting anything other than localhost

What type of issue is this?

Question

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Target SharePoint environment

SharePoint Online

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

• browser version
• SPFx version
• 1.22.1
• Node.js version
• etc

Issue description

I am trying to test a webpart on a SharePont online workbench from a different machine than the development SPFx is running on.

adding debugManifestsFile=https://somewhere.com:4321/temp/build/manifests.js used to work but now seems to be ignored unless it is localhost with some port.

I can look in the developer console and see that it doesn't even try to load the manifest from that url and instead reverts to localhost.

I know the property is being set correctly because if I do localhost with an obscure port like https://localhost:4444/temp/build/manifests.js it does indeed try to pull the manifest from that port.

I thought it could be related to CSP changes and added the domain (like https://somewhere.com) to the trusted scripts but that didn't have any effect.

Is there another setting to get it to pull the manifest from somewhere other than localhost?