@Yasai-san I've submitted PR's to update the patch we use for the XU4 defconfig in LE13 (2025.04) and LE12 (2024.01). I've not boot tested either defconfig but the problem and fix are obvious (hopefully). The LE12 change can be cherry-picked for Lakka to resolve the issue for Lakka v6.x too.
Thanks for the report and the detective work. I guess it slipped through the net as a) few people use the XU4 image with LE these days, and b) the few that do use the XU4 image probably first-installed an older release with working u-boot and then updated to newer OS versions over time, and updates don't touch the u-boot version.
EDIT: I've not seen your patch until after I've submitted the PR's to our repo. It's better to regenerate the whole patch against the upstream u-boot source as u-boot make periodic "resync" changes that change/move items around in the file. This time I also made some cosmetic changes to the XU3 defconfig too; the idea being that future resync changes might cause the XU3 patch hunks to break and thus flag the need for the patch to be updated again (although it's a long-shot).