Are you talking about “one” encore file, a few of them of a whole bunch?
For a small number, you should try to make a friend who has a working version of Encore (even if it is on a windows machine!).
Now, this is not everything. The XML support in Encore is very much outdated, and this particularly kills if you have lyrics.
A migration path would include making a PDF printout, which can often be converted using PDFtoMusic Pro. In evaluation mode you can freely convert one page at a time.