How to set SAPUI5 version to LTS in Cloud Foundry portal?

Dear experts,

we are currently hosting our Fiori lauchpad on NEO portal. When trying to move to Cloud Foundry, we have regressions in our Fiori apps from latest SAPUI5 1.77 which is used in Cloud Foundry portal service.

How can we set the SAPUI5 version for Cloud Foundry portal service to LTS 1.71? I cannot find a setting in Cloud Foundry website editor (like in Website configuration of NEO portal) or even in SAP Help Guide.

Best regards
Alej