The EO111 is being turned into A122 (or A121? The one it's not is some other urban Thessaloniki route. Hence the A123 number for the short stub after the A24 concurrency - it's what it's planned to be, but I jumped the gun). So signage would be patchy even with current GMSV - the final signage is to come next year.
EO111 is definitely the ring road, which is what the Greek means (its not 'Ring Road' as its name here for the same reason that we use Autovia not Motorway, etc). But so is the A24 (which isn't motorway on GMSV, but was the first bit upgraded) and I followed OSMs names in lieu of anything else.