When Ignition’s server is only configured with Basic256Sha256 SecurityPolicy then most clients will need to be configured with the “discovery” URL, which for Ignition is opc.tcp://hostname:62541/discovery.
To get UaExpert connected you’ll need to be using the latest version (1.5.1) and use this discovery URL and the “custom discovery” option, not manually configure the endpoint details.
Kepware’s client is broken and unable to connect unless the “None” SecurityPolicy option is also configured.