what's the easiest way to include the latest KB4103721.msu package into the Win10 RTM 17134 ISO that I got earlier from the MCT
Research how to use DISM. Its worth figuring it out on your own, its not super complicated. When I got into building my own images I started here and it really wasn't that hard.
Although @nosirrahx makes a valid point, answer would be: W10UI. Works nicely: https://forums.mydigitallife.net/threads/windows-10-hotfix-repository.57050/page-292#post-1435669.
Alright, now that an official CU is out: I still can't find it using Windows Update. It just installs Windows Defender signature and Office updates. I'm on 1803 17134.1 Enterprise and used an ESD -> ISO Image to do a clean install. Any ideas?
Yep, me too. But it does show up on WU when configured to use WSUS. I waited for 4-ish days for 1803 to show up on WU, but it never did.