by converting object parameter to JSONTemplate in the below commit
0053156#diff-799ddc34b2296767ac7f9fa14bae6050609a104930ded4de787dfdb7f49e50cbL97

the angular port of unlayer cannot use the legacy template loading as described in the official docs
https://docs.unlayer.com/docs/legacy-templates
https://examples.unlayer.com/web/legacy-template/