The OTA for global version 11.0.6.8 is out, but only the incremental OTA not the full. As global use googles own OTA servers and these servers do n ot provide full OTA for every update just the major ones. So you will have to wait untill Oneplus post the full rom on their website, which they apparently are very slow to do, if they do it at all. While EU and IN use oneplus own OTA server and get full OTA each time.
Unless you really want to keep global for some reason, I would suggest to convert to the EU version. Which get full OTA each time.
Or you need to do as
@Steve0007 posted in the post above mine and remove root and then install incremental update.