@JChildsJCMH,Thanks for posting in Q&A.
From your description, I know that you are looking for a way to lock down an Android device to a single URL via Intune.
Based on my research, we can create an app configuration policy for Microsoft Edge or Google Chrom and define a list of allowed URLs to achieve this.
Here are some steps you can refer.
1.Click App configuration policies > Click Add and select managed devices > Specify a name, select Android Enterprise as platform, select Fully Managed, Dedicated and Corporate-Owned Work Profile Only as Profile Type > Select Microsoft Edge or Google Chrom as Targeted app.
2.In Settings section, select Use configuration designer as Configuration settings format > Click Add and select Define a list of allowed URLs and Block access to a list of URLs > Enter the URL you want to allow.
3.In Assignment page, assign it to user or device group > Click create.
Note: you can block all URLs via Block access to a list of URLs and configure one specific URL in Define a list of allowed URLs to achieve this, because URL Allowlist works with URL Blocklist, it as exceptions to URL Blocklist, moreover the allowed list takes precedence over the block list.
Here are some links about how to configure URL format you can refer.
https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies#define-a-list-of-allowed-urls
https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies#block-access-to-a-list-of-urls
Hope above information can be helpful.
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