Here is SoapUI official github repository: https://github.com/SmartBear/soapui
It would be great to community do some step up to get some relevant things available for SoapUI open source. There is already pull request to fix this mildly annoying bug to detect correct response editor based on content type. Now in latest 5.7.0 version SoapUI pretty much always prefers to show raw response data as first.
However biggest issue that I see personally is that SoapUI Open Source does not support OpenAPI3.x.x. OpenAPI3 has been available for a long time and it should be included to SoapUI open source.