I have bought a new Samsung S9 from Mobilephonesdirect and I received this on Saturday. However, since I put the sim card in it has only said " Sim not provisioned" and gave me a MM logo at the top. I have contacted o2 on the live chat who took my Email address, name, home address but said...

Just flashed this on my S7, seems very good. https://forum.xda-developers.com/galaxy-s7/development/rom-s7-rom-v1-0-t3356197 Basically a slimmed down rooted version of the stock rom.