Problem with Greek language!

My initial thought is that some skins are not setup or translated for the Greek language.

If everything works well with the default skin (Estuary) then you will need to contact the maintainers of the failing skins - and/or by assisting in translating.

Also select the Arial font in the Kodi GUI. This is an option in Estuary and perhaps other skins too. That font holds many more characters.

It's not the Greek language, your custom skin just needs an update to work on LE 9.x.x (missing texture files):

2020-03-21 15:00:48.704 T:140011197126848  NOTICE:   load skin from: /storage/.kodi/addons/skin.aeonmq8 (version: 2.9.0)
2020-03-21 15:00:49.116 T:140011197126848 WARNING: Trying to add unsupported control type 1
2020-03-21 15:00:49.161 T:140011197126848 WARNING: Previous line repeats 3 times.
2020-03-21 15:00:49.161 T:140011197126848   ERROR: Control 9000 in window 10000 has been asked to focus, but it can't
2020-03-21 15:00:49.379 T:140010747717376   ERROR: DoWork - Direct texture file loading failed for resource://resource.images.recordlabels.white/
2020-03-21 15:00:49.383 T:140010756110080   ERROR: DoWork - Direct texture file loading failed for resource://resource.images.studios.white/

If you want maximum stability, use the default skin.

Quote from mglae

A bug in resource.language.el_gr causes Kodi to crush in certain skins.

Yes, a combination of custom skins and translation files is a possible cause.

@ LE developers:

I suggest to rework the LE code to make it more error-tolerant against incomplete skin / translation files. LE shouldn't crash in such cases.

I suggest upstream translators don't do a half-arsed job with their translations. It's the correct and darn sight easier approach

Quote from chewitt

I suggest upstream translators don't do a half-arsed job with their translations. It's the correct and darn sight easier approach

I always try to think from users perspective while programming: When LE just cashes, users think you're the bad boy. When LE doesn't crashes and pops up a toast "Incomplete translation / skin", then users know the real bad boys, and can address them. Isn't that great?

It's worth to program all the if's and then's, because bad translations and skins will never die. Doing some tests before allowing an add-on to be uploaded might help, too. You already do add-on quality control to avoid illegal stuff.