The realme GT Snapdragon 888 is made by Samsung.
The Snapdragon 888 equipped with the realme GT uses Samsung's 5nm process, Qualcomm Snapdragon processor is produced by Qualcomm, outsourced to China or Vietnam some OEM manufacturing companies, the Snapdragon 888 chip manufacturing should be made in South Korea, but the name is changed to this for the Chinese market.
Made by TSMC, the company that makes the Snapdragon's processor. The Snapdragon 888 processor used in the realme gt is also made by TSMC.