George Lynch (1868-1928) was listed by Sprague deCamp[0194.329] as a supporter of a Brazilian Atlantis in 1925. Until recently, that was all that I could find about him. However, I discovered that Stelios Pavlou had unearthed much more information.
Lynch was an Irish war correspondent, reporting on conflicts such as the Spanish-American War, the Boer War and the Chinese Boxer Rebellion* and recounted in his Impressions of a War Correspondent .*
Towards the end of his life, Lynch was a fund-raiser for Percy Fawcett’s expedition to find the lost city of ‘Z’ in Brazil, which, apparently, they both believed to have a possible connection with Atlantis.
Brazil has had few serious investigators propose it as the location of Atlantis. Although, in 1947 Harold T. Wilkins claimed[0363.97] that Quetzalcoatl was from Atlantean Brazil. Earlier in the 20th century, Col. P.H. Fawcett, the famous explorer, disappeared while searching in the Brazilian rain forest for a ‘lost city’ that he called ‘Z’. A 2009 book by David Grann about Fawcett’s searches in Brazil, entitled The Lost City of Z  was the basis for a film released in 2016. Sprague de Camp listed[0194.329] a George Lynch supporting a Brazilian Atlantis in 1925. In fact, Lynch was a fund-raiser for Fawcett.
However, although there is growing evidence of ancient roads, plazas and bridges in Brazil’s vast tropical forests, further data is needed before we can attempt to fit these structures into any specific culture or chronology.
An article(e) in the August 2017 of Antiquity offers evidence that humans lived in Brazil more than 20,000 years ago, which is many millennia before the Clovis people arrived in North America.
The possibility of Phoenician contact with Brazil has a number of supporters and a range of websites supports this controversial view(a). One such advocate, Ronald Barney, maintains that they concentrated their influence in the northeastern region of the country citing the work of Ludwig Schwennhagen and Apollinaire Frot(f). There would appear to be evidence for 3rd century AD Roman contact with Brazil(h).
May 2013 saw a flurry of media interest when a Japanese submersible found evidence in the form of granite suggesting of a previously unknown continental mass that sank about 900 miles off the coast of Rio de Janeiro. Members of the expedition have played down any attempt to link this discovery with Atlantis(b)(c).
This reminiscent of the reaction in 1931 when two islands were reported to have emerged from the sea off Brazil and within a short time, claims that they were a returning Atlantis were widely quoted(d).
Any suggestion that the land of Hy-Brasil in Irish mythology has any connection with Brazil or Atlantis is just wild speculation.
(g) See: Archive 3480