Nitrokey Update testrelease not working

According to Releases · Nitrokey/nitrokey-3-firmware · GitHub i tried to update my nitrokey 3C

$ nitropy nk3 update --version v1.5.0-test.20230704
Command line tool to interact with Nitrokey devices 0.4.36
Do you want to download the firmware version v1.5.0-test.20230704? [Y/n]: y
Critical error:
Failed to find firmware image for release v1.5.0-test.20230704
	Exception encountered: ValueError("Failed to find asset for release v1.5.0-test.20230704 matching re.compile('firmware-nk3-v.*\\\\.zip$')")

Cool… it does not work.

Then i tried to download the zip and install it

$ nitropy nk3 update nitrokey-3-firmware.zip 
Command line tool to interact with Nitrokey devices 0.4.36
Critical error:
Failed to parse firmware container
	Exception encountered: KeyError("There is no item named 'sha256sums' in the archive")

--------------------------------------------------------------------------------
Critical error occurred, exiting now

In the archive is this file nitrokey-3-firmware/utils/nrf-bootloader/sha256sums.txt