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I looked at the Tithe listings for Co. Donegal from the late 1820s and did not see a George Cunningham record. I think it is possible that your George was one of the three listed in the Griffiths. I took a look at the 1901 census records for those townlands and based on the religious denominations of the families, I think that Edegole and Urbal are more likely. There was a Cunningham family in Urbal http://www.census.nationalarchives.ie/pages/1901/Donegal/Galway/Urbal/1168345/ but we can only speculate about any connection to your family.
There are no Hugh Cunningham baptismal records with a father George on the subscription site Roots Ireland.
I looked at death records. Currently the free site www.irishgenealogy.ie has images of death records from 1978-1969 and for deaths from 1864-1877 there are index records although at some point in the future images will be added. I looked for George Cunningham records and found two of interest. There was an 1870 index record in the Donegal registration district which is likely for the George in Edergole. There was also an 1892 record for the George who was from Carrickfin. That record showed he was still married but I did not find a related Elisabeth death record after 1892 which to me eliminates Carrickfin.
NameGEORGE CUNNINGHAMDate of Death1870Group Registration IDN/RSR District/Reg AreaDonegalDeceased Age at Death67Returns Year1870Returns Quarter2Returns Volume No7Returns Page No27
Seventh record https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1892/06036/4718995.pdf
Let me know what questions you have and you may have interest in this article https://irelandxo.com/ireland-xo/news/irelandxo-insight-how-dna-can-help-you-connect-ireland
Roger McDonnell