ldproxy Swagger page does not load

[justb4]

https://apitestbed.geonovum.nl/ldproxy/RCE_Landschapsatlas_WFS/api/?f=html remains blank.
In JS console the following errors are shown:

apitestbed.geonovum.nl/:1 Refused to execute script from 'https://apitestbed.geonovum.nl/ldproxy/RCE_Landschapsatlas_WFS/api/swagger-ui-bundle.js' because its MIME type ('application/octet-stream') is not executable, and strict MIME type checking is enabled.
apitestbed.geonovum.nl/:1 Refused to execute script from 'https://apitestbed.geonovum.nl/ldproxy/RCE_Landschapsatlas_WFS/api/swagger-ui-standalone-preset.js' because its MIME type ('application/octet-stream') is not executable, and strict MIME type checking is enabled.
?f=html:41 Uncaught ReferenceError: SwaggerUIBundle is not defined
    at window.onload (?f=html:41)

Swagger works e.g. ok for pygeoapi
and for GeoServer.