Unfortunately, no longer able to be updated.
Good article on the status of Roku models that can and can't be updated with Roku firmware or software.
https://www.cordcuttersnews.com/roku-is-ending-support-for-older-models/
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941