UI Toolkit is broken when going down from 2021.3 to 2021.1

Unity Engine
,
1

Hi!
I built a tool using UI Toolkit that come with 2021.3
the tool itself is great and intuitive.

However, nothing works when going down to older versions, I did work on (2021.3, 2021.2)
but anything earlier than (2021.1) dosen’t seems to work

I can see that even the generated uxml is different.

is there any way around that,
or do I have to rebuilt it for every older versions?

Have a good day!.

2

Content authored in newer version of unity is not expected to work in older version. It could work, but there is no guarantee in this regard.

The opposite should work (bringing old content to new version of unity) but you may need to follow these steps : UI Toolkit migration guide