I hope you're able to get your internet working in Greece soon! I'm actually planning a trip there later this year and was worried about having the same issues. Let me know if changing the TTL works for you. I may have to try that as well if I run into any blocking from Cosmote. I'm also new to trav...

Try the free version of Ekahau Heatmapper. It's not perfect working on a floorplan vs in-situ, but may give you a better idea than nothing. Another option is putting the APs high up on ladders first before committing to ceiling mounts.

It's definitely worth trying to remove the FT settings from your cfg-TIMT configuration, that could be causing issues getting clients to connect reliably. And good callouts on double checking that your datapath and bridge setup looks okay - if devices aren't getting DHCP it would explain them droppi...

It looks like you've got all the pieces set up individually, they just need to be tied together on that bridge. Frustrating when it's the "last step" keeping it from working!