I'm pretty sure the brick was not a fault of the user, but rather a poor implementation of the web update on behalf of Siglent.
@Kibabalu: I would like to know what exactly happend and what you did? Did you just select "online FW update"? Did you have a USB disk inserted? Did you remove it after first reboot?
The procedure was:
1. download the FW on my machine (iMac)
2. selecting the online FW update offered from the web Front end inside the browser (Safari)
3. choosing the downloaded FW file (iMac)
4. reboot
5. brick!
The manual is stating very clearly, that a FW update has to be made by using a usb stick and initiated by the menu function of the unit, otherwise you loose warranty.
Thus, no question, it was my fault. I haven’t RTFM ;-)
But on the other side, siglent should not offer such a „trap“ inside their web front end.
In general, the web front end seems very sloppy when using browsers under macOS (tested with Safari and FireFox). It's sloppily developed, means they do not test properly, e. g. testing all functions against other operating systems than Windows too.