Using Outlook for Android in business environments for email and scheduling
My suggestion might not be the solution but it's what I would check not knowing how you have things configured.
It sounds like you might have used aliases for Gmail and Comcast in your Outlook.com account. I think older protocols might have allowed sending from Comcast or Gmail from Outlook.com, especially on mobile devices. This won't work with newer protocols on devices or Windows. Something you should check is what aliases you have for your Outlook.com account e.g. your live.com account. Go to this page and make sure the live.com address is the primary alias, https://account.live.com/names/Manage. Do not remove any alias from this page. It's an unrecoverable action and it is safe to have other aliases listed here. You might have used one of those aliases for signing in to other sites or to buy Microsoft services or software.
If you have Comcast or Gmail as aliases listed there you can verify them and then send from them from Outlook.com on the web. However, when you send from an alias it will show as ******@live.com on behalf of ******@gmail.com.
The best path I can suggest would be to add each of the accounts Live.com, Gmail.com, Comcast.com to Outlook for iOS or Android on your device. On Windows do the same by installing New Outlook for free, The New Microsoft Outlook for Windows | Microsoft 365.