If you mean on rails by train-there is NO other way onto EUR-you can get onward in TR-if lucky to find empty seat at short notice, on the Turkish TCDD hi-speed trains to Ankara or Konya.
This line has always been the one and only into west-EUR-but in the past with several other service (once even as far as Múnchen), Seat61.com is best site for current tips/hints/routings-and do be aware that there are NO trains over borders to GR nor the former Yugoslavija parts, like Serbije, Macedonia, etc.
An other way is via Sofia-KUlata (border)-bus/taxi-to first stop in GR-hen via GR and ferry over to Italy
The Sofia-Istanbul Express resumed operation in April 2022 and should still be running. You can find more information about it here. The timetable should be available on the Turkish carrier's website and reservations can be made locally at the station. Please keep an eye out on the carrier's website for travel contingencies.
Take the train from Istanbul to Sofia, then take a bus from Sofia to Skopje (there should be several departures per day).
From Skopje you could take a train to Kosovo (if it is running) or go via Ohrid Lake to Albania.
Then you can make your way to the coast in Montenegro and from there get a bus to Dubrovnik (Split) - although not sure how frequent they are in off-season.
From Split you can make again use of your interrail.