I have been informed about this plaque by a viewer, who wrote: "The plaque is possibly affixed to a house commemorating "the renowned explorer" Sandor Körösi Csoma who stayed in Aleppo for a month in 1820 on his way ("pilgrimage") to Tibet. It was obviously sponsored by the Hungarian Academy of Sciences, and is entitled "In search for the origins of the Hungarian ethnicity".

I next looked in the Wikipedia as the viewer suggested and found: "Sándor Kõrösi Csoma (March 27, 1784 – April 11, 1842), born Csoma Sándor, also known as Alexander Csoma de Kõrös, was a Hungarian philologist and orientologist, author of the first Tibetan-English dictionary and grammar book. He was born in Kõrös, Transylvania. His birth date is often credited as April 4, which is actually his baptism day. Hoping that he would be able to trace the origin of the Magyar ethnic group, he set out for the East in 1820, and after much hardship along the way, arrived in Ladakh. Under great privation there, despite being aided by the British government, he devoted himself to the study of the Tibetan language. He made the first English-Tibetian Dictionary while living at Zangla Monastery in Zanskar in 1823. The dictionary was published a year later in 1824. In 1831, he settled in Calcutta, where he compiled his Tibetan Grammar and Dictionary and catalogued the Tibetan works in the library of the Asiatic Society. He died in Darjeeling just as he was setting out for fresh discoveries. He is said to have been able to read in seventeen languages. De Kõrös is widely seen as the founder of Tibetology." and a bit further: "On March 15, 1820, he sails to Latakia via Cyprus, Beirut and Tripoli. From Latakia, he continues on foot.
On April 13, Csoma arrives in Aleppo, where he stays for a month. "