Ok so I've just used odin to flash my phone onto XEU from H3G however I'm still getting the Three boot logo? When I did this on my S7 for the Oreo beta I got the samsung boot screen after flashing. I'm now on xeu/xeu/h3g.
I had the same. I backed up. Done a hard reset and the 3 logo disappeared. I will day though my phone wasn't originally from 3. I only flashed it to use the supervoice and WiFi calling but since doing that ⬆️ supervoice and WiFi calling works with XEU/XEU/XEU.