Ladies and Gentlemen...I found our iPhone 11/11 pro/11 pro max LOOPHOLE
I DID IT. I found a way for your unlocked iPhone 11 to work with Boost.
(Quick disclaimer: I spent many hours with customer support as well as Apple support and as a person who kinda works in this industry, the idea popped into my head. At the time of writing this, my phone (11 pro) is able to make calls and the 4G LTE is working like a freakin' charm.)
Now, I purchased the 4-in-1 sim kit from boost, but you can get a free sprint sim card from Apple. Put the new sim (Part number: SIMOLW516TQ if you purchased the Boost sim kit) BEFORE you turn your new phone on. Call Boost Customer Service on a secondary phone (like a household phone) and tell them that you bought your new phone with a Sprint sim inside! They will ask for your IMEI and ICCID on your new device and to tell you to turn your current phone off so they can transfer the service to your new device. That's it.
I hope this helps.