while all of those work and I can initiate the U-Boot TFTP procedure properly (as in keep reset button pressed while powering on / watch led flash rapidly / release button), no firmware.bin gets requested by 192.168.10.101 which is the wavlink's tftp client ip address.
thanks, this works, you get telnet on port 2323, credentials are admin/admin.
following Connor's tutorial, cgi-bin/upload_bootloader.cgi is missing. Connor was kind enough to upload a WN575A3 version of the file here. Do not forget to chmod u+x it and put it into the right place as Zheng Jie Tan kindly shows here. I was able to upload the missing upload_bootloader.cgi using upload.cgi as described by Zheng.
But maybe it is not fully compatible with a WN570HA1 since its taken from a WN575A3 image. It accepts the unlocked Bootloader.bin and reboots after the upload, but TFTP still does not request a thing.
I have reflashed the oldest stock I could get back from 2017, but also there is no original upload_bootloader.cgi in the blob.
A somewhat exciting scavenger hunt on a 20 € eBay classifieds device, but TFTP did not happen yet.