Hi @matfax,
Well, after all the issues I had, none seem to be related to u-boot. So I can not provide first hand info - but I came across Boot Rescue is broken - #8 by miska maybe it will help you, before you need to solder…
Thanks to the work of the turris team! I do see progress - and I hope to see the new device this year.
Thx,
Vienna
EDIT: Currently using U-Boot 2024.10-rc3-OpenWrt