I read his name in the RCEs as Jozas, not Joyas, which matches his name as in the newspaper extract.
I also agree that he is probably Lithuanian. Many male given names in Lithuania end in '-as' and Juozas is the standard Lithuanian equivalent of Joseph.
Lithuania came under Poland at times, and parts of it under Russia at other times.
As for the number of aliases, all except 'Robert Hunter' look pretty much like Juozas Linka, and can probably be ascribed to people not being familiar with the spelling of his name, or him wishing to anglicise it for the sake of simplicity.
That 1973 death is registered as Robert Hunter as well as Jozef Linko. The death certificate should tell you his date of birth and the names of his parents including his mother's maiden surname, assuming that the informant knew their names.
If his mother's surname ends in '-iute' or '-iene' you can be pretty certain that he was Lithuanian. An unmarried woman in Lithuania has a surname ending in '-iute'. When she marries, she takes her husband's surname, but replaces the final '-as' with '-iene'.
These practices usually got a bit mangled when confronted by a Scottish Registrar unfamiliar with the practice or the standard spellings of Lithuanian personal names.
