I found a solution:
delete all javafx_*.jar in /Applications/SoapUI-5.7.0.app/Contents/java/app/lib

then install Liberica JDK 16.

brew tap bell-sw/liberica
brew install --cask liberica-jdk16-full

now soap-ui is working

Hello aescobar & PhilipF and other community members,

I'm Yousaf from the Developer Relations team here at SmartBear

Firstly, thanks for your patience!

We can confirm this is not a malware issue. 

This issue was also tracked via GitHub & StackOverFlow as well. Apologies for not updating here sooner!

We are pleased to announce that we now have a new release 5.7.1 out.

SoapUI Open Source 5.7.1

Released on 2023-08-01

Fixed an issue where SoapUI version 5.6.0 and 5.7.0 would not install or open on certain machines including Mac OS Ventura. There were issues with an expired Apple Certificate and previous bundled JRE environment. We have signed the new version with updated Apple Certificate and also updated the bundled JRE environment to Liberica version 16.0.2+7. These updates which resolves this issue for Mac users and the application now installs properly. Windows and Linux versions also received updates to the bundled JRE environment.

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Links are below

1. GitHub Release SoapUi 5.7.1 
2. Release Notes
3. Official Download Page 

Thanks again for using SoapUI and bringing the issue to our attention.

Saf