I am starting this thread to document the process of building and testing u-boot on the MangoPi QUAD H616. It may work for other boards as well. The original link for this process is largely written in Chinese, so hopefully this provides insight as to how to do it, as the original web page has omissions and errata.
This image I am starting with is the partially updated bookworm image built in:
Journal: Debian Bookworm build for MangoPI quad H616
The initial article is based on:
MQ-Quad H616 Mainline Kernel Compilation and Debugging Records (u-boot, kernel, buildroot)