if nand-sata-install is not maintained is there a replacement

Nope, my build is based on current mainline and even build on target (aarch64). I.e. no cross-compiling involved. Oh, by the way, in my build bootstd scans any attached storage for a valid bootflow and uses the first found one. The used hardware interface dosen't matter and even network is valid.

After a lot of attemps with kernel versions and so on without any result this is the simple solution: Buy an USB to analog adaptor for 6 euro's brand MOSWAG, that's all folks.

You're using Hardkernel's U-Boot. Yes, it's probably more importent to read from flash memory early, at boot. Using the manufactors bootloader is the only option until the chip or whatever is supported "mainline". If one doesn't care about flash, but doesn't want to depend on SD card to boot from e.g. SATA, an option is to run Hardkernel's Linux, once to write U-Boot to NOR flash . kexec seems to need CONFIG_PROC_KCORE, but Armbian as many others doesn't. Mainline U-Boot doesn't load Hardkernel's Linux. Perhaps just boot the spiupdate.img without spiboot.img and run. (sounds strange I know, but better than cross-cross-compile out-of-date) Any news on mainline (patched) support for SPI NOR flash on Odroid-HC4? Perhaps I miss just a simple thing?

That error with mkimage during nand-sata-install is fairly common on XU4 and usually harmless if the system boots fine afterwards. The tool is a bit outdated and often throws this warning even when U-Boot is written correctly. Since it’s working after reboot, I wouldn’t worry about it.