Thank you for the information.
There is a Canon PRINT Inkjet/SELPHY app for iOS.
https://apps.apple.com/us/app/canon-print-inkjet-selphy/id664425773
Unfortunately, I cannot find anything indicating that the MP499 model is supported (for example, an MP495 appears to be). You could of course try it anyway, but do not expect it to work.
The only other option, without a working app from the printer manufacturer (and without AirPrint support), may be to look for (and experiment with) another (third-party) iOS app in the App Store. What did you use for the iPhone 8 test print?
Do you still have the faulty 2010 MacBook Pro? If so, is it totally out of order? Cannot be repaired? As you also already know, a Mac application such as Printopia would have allowed an OS X 10.9 Mavericks or later Mac to act as a print server for printing from an iPhone.