Help for newcomer to Interrail (82 y.) to get to Greece

The rail network in the Balkans is not the best in Europe, the best way to get to Greece by train is probably to get to southern Italy and take a ferry from there. As usual, The Man in Seat 61 is a good place to find answers: https://www.seat61.com/Greece.htm

Oh I wish you had asked about trains in and to Greece before spending you money. I'm afraid that that part of the trip may be difficult.

I'm surprised that you bought Interrail - for European residents - rather than Eurail which is for foreigners. If you aren't used to European trains or European prices it doesn't sound to me like you would have been a prime candidate for Interrail.

Or if you have moved to Geneva very recently I'm concerned that September is well past the 90 days allowed unless you have European citizenship? Do you have a clear understanding of the Schengen requirements?

Seniors of all ages are welcome, even with open arms, at most youth hostels. Most have even dropped the word "youth" from their names.

PS to my last post: If possible I would like to start my journey by the little Centovalli train from Brig in Switzerland to Domodossola, and take it from there, to Greece or whatever.
And a travel trip from me: the Centovalli run is the most charming journey I have ever experienced, but it is essential to do it on a fine day.

Thank you very much for your info, Badger. The Man in Seat 61 website you recommend is fabulous, and I will be very happy to travel down the eastern coast of Italy to Bari. So that's on the cards

Nigel, I’m not sure what you refer to as difficult. If I can get to Greece from Bari after travelling down the east coast of Italy, there should be no problem, no?
And I really am a European resident, a Brit living in the Drôme department of France. Geneva is where my son lives, and from where I would begin my journey in the first days of September. So that aspect seems to be OK.
Thank you too for the open arms. Despite my 81 years (will be 82 when I travel), I feel young enough to justify the use of Youth in the title :-)

Correction to my earlier post:
And a travel tip (not trip) from me: the Centovalli run is the most charming journey I have ever experienced, but it is essential to do it on a fine day.

If I may repeat my earlier question:
Am I right in thinking that it is easy to find walk-in homestays in southern Europe?