I found out on how obtain a Yellow Card in Ethiopia.
To get a Yellow Card from abroad, if have family members, you will need get a power of attorney (POA) for them speak on behalf get all the required documents need in Ethiopia that your Ethiopian origin. Most of documents need be produced in the local region.
Contact local Ethiopian Embassies in your home country regarding POA Option.
If you decided go to Ethiopia your self, first port call will be your local regional government authorities, will give you guidance what to do, Diaspora office will help.
Remember, it will take maybe 2 months get all required documents by POA) in person it can maybe same time too.
Then, your option when your in Ethiopia you can get Yellow Card from capital Addis ABABA) It will take 7 days i was told.
other option, will be by POA) get all documents sent to you apply at Embassy) remember all documents need be translated in (amharic) and stamped by local courts in your region
My advise use DHL when get documents sent to you safe and very fast. In Europe it will take 5 days and rest of the world maybe 8 - 10 days. Embassy option will take 4 months get your Yellow Card.
Ethiopia has 9 national regions, 2 City administration. All regions have there only language important that documents are translated in amheric.
I hope my information does help regarding how to obtain a yellow card from Ethiopia and if overseas by POA) though family members.
Regards