@MatthewRiddler-9775 The server where you have installed the App Proxy Connector establishes outbound connection to the App Proxy Service in Azure. It sends all Cipher Suites (enabled on the connector server) in the client hello during TLS Handshake and in server hello, the Azure App Proxy service responds with the cipher suite which is strongest and common between them. So, in order to remove the use of week ciphers, you can disable them from the App Proxy Connector server.
Please do not forget to "Accept the answer" wherever the information provided helps you. This will help others in the community as well.