I’m sure that’s very frustrating. It sounds like you’re taking the right approach.
First, just to get this out of the way, do you have other devices working via Matter on your SmartThings account? It might be worth quickly skimming the matter FAQ if this is the first matter device you’ve tried adding.
I know there have been some community members who did get the ZemiSmart Matter bridge working with SmartThings, but I don’t know the details except in one case the person did not originally have IPv6 support turned on on their WiFi router.
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?
If you do have other matter devices working on your SmartThings account, and the firmware on your zemismart device is up-to-date, but the QR code being generated in the tuya app is not being accepted, then you should get in touch with ZemiSmart support and see if they have any suggestions. 
Hopefully someone here who has it working will post more details.
In any case, as I mentioned above, you will never be able to add new Zigbee end devices to the ZemiSmart matter bridge using the SmartThings app. You always have to go into the app and add the new Zigbee devices there so that they can then be bridged into SmartThings.