Apologies up front if this has been addressed ad-nauseum, but I wanted to see what people have done about the knocking (detonation / low-speed pre-ignition) at lower RPM's in the 2019 5.0. Is there any other solution aside from running 93? It does work, but these days it's not all that attractive an option. And why is 87 recommended for this engine??

Thanks!
(newb)

 

My 2018 with the same engine has no issue with 87 and now switched to 88 unleaded/ no ethanol, the lowest expense fuel in my area. Fuel mileage is very good.
Questions, comments and some things I would do.
Did you give the system enough time after switching to 87, to adjust the fuel and timing tables? 93 to 87 is a big one jump change. There is a Knock sensor that detects ping and knock. It retards the ignition timing to minimize ping and knock and becomes part of the adjustment record the software makes to the fuel and timing tables. It may take a full tank usage or more to achieve results because no system can adjust very quickly unless the system is Flex fuel designed. with fuel sensor detection.
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For me, I would track live data with a Scanner and would look at the ignition timing for the retard and a look at the long-term fuel tables for shift % in the lean direction. Then there is EGR function that could cause your engine sensitivity to throttle load changes.
I offer this as what I do but not expect the casual owner to know about or have such tool.
Why is any engine sensitive to Octane changes, especially those with high compression ratios such as the 5L.?
The reason is not in fuel power in BTU but the change is flame speed during combustion. This means a change in the Ignition timing progression. To fast = ping and knock result. Lower Octane is faster. The program has to adjust/retard enough..
Unless a cause is uncovered, there won't be an easy answer or clues from code-set.
Reason is the system operation is not outside program limits so no fault code would be triggered.
Not a fix for you, but some background to offer.
Good luck.