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.
I can confirm that this works.
Last night I purchased an iPhone 11 Pro from the Apple store. I asked for an unlocked phone and the salesmen told me all of the iPhone 11s are sold from them unlocked now. I also asked for a Sprint SIM card, which is free. You'll note that the SIM card also says Boost Mobile on it.
I put the sim in the phone and sent a text to boost mobile on another phone to #2781
I gave the ICC ID from the SIM and the IMEI from the phone box. I also gave the number and pin of the phone that I was transferring service from. They asked if this was a phone I bought from another carrier, from Apple, or from Boost. I replied it was from the Apple store and that I saw on the forums that they will activate Apple store phones now. The next response was, "Your device swap has been completed".
Hey there, burningquestion! If your device is from Sprint and it is unlocked, we can activate it.
We understand your frustration, @vebalcazar, & we apologize for the inconvenience! We value your privacy and security. Due to the nature of your concern, we would like to authenticate your account, but for us to do this in a secure way we need to take this to a private channel where we can discuss private account information. Please send us a private message along with your phone number, the PIN and a brief description of your request. To send a private message, click on any of the social care agents user names and select the option send this user a private message.
I tried this method, and it unfortunately didn't work. Boost led me on a wild goose chase. As seen in this discussion forum, a Boost Rep said sprint unlocked phones could be activated. I messaged them and I received a different message from a different rep stating that they do not activate unlocked sprint iPhone 11's, Boost could only activate unlocked iPhone 11's from the Apple store. I called Boost mobile with this information and they said they were not unlocking iPhone 11's whatsoever. I decided to do the text Boost method, and they only mentioned to check out the compatibility on their website or go to a Boost mobile store. I went to the Boost mobile store and voila, they said they could activate BUT I HAD TO PAY $35, regardless that I had the appropriate SIM card for the iPhone 11 that was sent from Boost mobile to my residence. They said I had to buy the SIM card from their store in order for my iPhone 11 to be activated ($10) and $25 for activation. So there you go. Go to a Boost mobile store, they will charge you, but they will activate it.