(Engineer responsible for implementing the NDI plugin here)
I believe the 4.26/4.25 version did also work on 4.27 if you changed the EngineVersion in the .uplugin file and recompiled the plugin. I did recently find an issue with compiling it for UE4.27.2.
The release process of the NDI plugin is currently undergoing revision, and I honestly do not know right now what version of the plugin is available to the public.
We do have the plugin working with UE5 preview, and UE5 release just finished installing so I’m going to check if anything broke.