Does anyone know of any issues with using Citrix Receiver 4.1 against a Citrix Virtual Desktops and Apps 2507 environment? We still have a few clients that need to run it because of older hardware, so I’m looking to see what problems (if any) others have encountered.

SSL Certificates is the biggest thing with those older clients.

Official docs confirm compatibility with all currently supported Citrix Workspace app versions, explicitly noting older Receiver versions like 4.x "may work but are not supported." https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/2507-ltsr/system-requirements