Accessing SharePoint user profile properties via REST api (_api/SP.UserProfiles.PeopleManager) in SPFx stopped working as of May 27th @ around 7pm

Target SharePoint environment

SharePoint Online

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

SharePoint REST API

Developer environment

macOS

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

• Affecting all users in our company
• Various: Edge/Chrome/Safari latest
• SPFx version 1.17.4
• Node.js version 16.20.1
• macOS 15.4.1/Windows 11 etc

Describe the bug / error

There is an internal Microsoft support ticket attached to this.

Retreving a SharePoint user's profile properties via REST ap in SPFx stopped working as of May 27th @ around 7pm. The following code snippet will fail (mildly edited from what I have in code):

this.context.aadTokenProviderFactory.getTokenProvider();
                              .then(aadTokenProvider => { return aadTokenProvider.getToken(tenantURL) })
		             .then(token => {
				const requestHeaders: Headers = new Headers();
				requestHeaders.append("Accept", "application/json;odata=verbose");
				requestHeaders.append("Content-type", "application/json;odata=verbose");
				requestHeaders.append("Cache-Control", "no-cache");
				requestHeaders.append("Authorization", `Bearer ${token}`);
				requestHeaders.append('odata-version', '');

				return this.context.httpClient.get(tenantURL + "_api/SP.UserProfiles.PeopleManager/getuserprofilepropertyfor(accountname=@v,%20propertyname='propertyname')?@v='i:0#.f|membership|username@userco.com'", HttpClient.configurations.v1, {
					headers: requestHeaders
				});
			})

Note that I use aadTokenProvider and httpClient instead of spHttpClient because that's the only way to access properties in a multi-geo tenant. This was working for both my main domain and my emea domain.

Steps to reproduce

1. Place the above code in a newly minted SPFx webpart
2. Test the webpart with gulp serve
3. Request will fail with Permissions Denied 403 error

Expected behavior

The httpRequest should be successful and return a value for the requested property.