Megacubo is a free and opensource IPTV (M3U) playlist player. With the application you can watch live TV channels and if you do not have IPTV lists, you can use it in community mode, thus receiving lists shared by other users.
The program contains channel lists in categories, by country, connection quality and genre, making it very easy to find the content you are interested in.
To set Megacubo to show only Greek channels you should click on Options > Countries. Make sure Megacubo is in Greek first, if it is not, you should set the language from Options > Language.
If you want to find playlists Google is your best friend. Search for IPTV Lists (M3U) and you will find as many as you want (also for Greek Channels).
According to the FAQ you can add as many M3U playlists as you want. Megacubo will process them all and search for the stream you want in each of them until it finds and opens one that can be connected.
Download the application on the platform you are interested in (v17.4.3)
https://github.com/efoxbr/megacubo/releases
M3U for Greek channels greek-iptv.
M3U for International Channels iptv-org / iptv