DHTMLX suite 6.4.2 xml support

Is xml still supported in the library or json only?

Can you show me an example loading with xml?

xml is supporterd in the PRO version only of the dhtmlxSuite 6.
Here you can find a tutorial a with the xml template:

Do you mean Data loading and column configuration is possible with XML as well?

I read it needs JSON. https://docs.dhtmlx.com/suite/grid__data_loading.html#preparingdataset

I use a PRO version and wanted to upgrade it to new version.

Config should be defined as a json. Only the data can be loaded as an XML.