Xiaomi, Vivo and OPPO launched a file-transfer system of their own in February 2020. This facility allows for a robust form of sharing between Android devices from these 3 OEMs independent of any third-party apps. Now, the additional brands Black Shark, Meizu, OnePlus and Realme have declared they want in on this action.
https://www.notebookcheck.net/Black-Shark-Realme-Meizu-and-OnePlus-join-the-multi-Android-OEM-P2P-file-transfer-alliance.466168.0.html