It's all carrier, so would I be able to have service on all 4 carriers?
Insert AT&T SIM = AT&T svc
Inset Sprint LTE SIM = Sprint svc
Insert Verison LTE SIM = Verizon svc
Insert T-Mobile SIM = T-Mobile svc
Yes, I have a relative who has the same phone primarily for Verizon use. However, when they went abroad they were able to use a GSM sim in that country. It is a very good not-budget-looking phone and even comes with a fingerprint reader.
Hm... which to get?
Moto G5 Plus 4/64GB for $225
or newer and bigger screen
Moto G5S Plus 3/32GB for $240
On a separate note, I hope this idea is implemented in dual sim phones too. That would be really cool, if it isn't a thing yet.
Costco has it for $210. Forget the size
Got this for $156 after tax on Cyber Monday... works fine for Freedompop LTE SIM but I cannot get it working on Freedompop Sprint BYOD nor Sprint Post Paid... reading online, I do not see a fix. I get this erroneous message "Sorry, but our records show you still owe Sprint for this device. Sign in to find this device on your account." phone CS does not know how to clear it - no outstanding balance, no FED flag...
Tested with Tello (swapped device on my existing Tello line)... success!
Swapped Tello back to my S6E+ so that Moto G5+ is free again.
Tried to sign up online for my Moto G5+ again... same error message... argh!
"Sorry, but our records show you still owe Sprint for this device. Sign in to find this device on your account."
Any other suggestions?
Hm... wonder if this is one of those Sprint Retail and Sprint Wholesale list thing combined with some weird glitch, like the reports of incompatibility in several April 2017 posts...
So I started by signing up with FP Sprint BYOD (wholesale side) first... never worked...
- when I tried to sign up for Sprint postpaid (retail side), I get the error message.
- when I tried swapping into Tello (wholesale side), it works.
One more observation... after successfully updating device profile/prl on Tello, it is showing preferred network as 3G and not LTE....
Wonder if this has to do with the "special SIM" that some posts mentioned... but that would not explain the error message from entering just the MEID on Sprint post-paid.
If you activated it on a sprint mvno like Tello the "flag" gets moved to prepaid mvno and you will get errors trying to sign up with postpaid. You need to get sprint to change the flag to postpaid. Technically it requires changing from PLBL to SPCS but they should understand you if you say prepaid to postpaid flag. You could ask tello to do it - they helped me a couple of times but it takes a few days. As sprint are the ones who actually do it so you could just ask them directly to speed it up if you are in a hurry.
On a side note Tello were pretty knowledgeable about it when I explained it to them the first time and even wanted to know how I found out about it all. Which was another positive sign from tello customer service!
You could also ask this reddit user LiterallyUnlimited as he/she is able to do it sometimes.
Not sure about freedompop byod - they might not like it being a carrier free phone? That one should work.
If it's a wholesale/retail issue (which I think Sprint terms as PLBL/SPCS), you can ask for a clickit ticket-- I've seen it recommended to do it at a Sprint corporate store that has a service department. If you can't find someone, there's a Ting tech on Reddit that's been doing this for people.
(Oops, I see mmfacemm posted a link to the Ting tech while I was typing-- now I don't have to look it up!)
Thx! Just missed Customer Service hours... will have to call tomorrow, I guess... 
Try using the Change APN app to reset APN to defaults, & reboot.
This seems similar to my issue at https://www.nthcircle.com/forum/big-four/1025-any-gotcha-with-sprint-1-year-free-unlimited-service?start=40#17305
Got a Click-It ticket in this weekend... guess they did not get to my ticket yet as of now. I was gold it could be 3-5 business days, so hopefully this week... time's a wasting. 
Some reps can do it instantly. It is very YMMV with sprint.
It's cleared! Signed up, waiting for port to complete.
Like the linked posts, my Moto G5+ shows up as 'ZTE Optik' on Sprint.