In order to maintain a backlog of Arria II based devices I would like to connect the data streams (fiber optics 2.5G) to newer Agilex based FPGAs. Is it possible to use old Serial Lite II protocol in newer devices? I do not see any reference past Arria 10.
The documents on Agilex E-tiles do mention Serial Lite, without any version number.
There is no IP for Serial Lite II protocol targeted to Agilex devices. You may have to do the manual transition to the Agilex.
You may find IP for Serial Lite IV for Agilex.