- Location
- Norway
Jules Verne originally wrote the draft with Nemo as Polish, primarily getting vengeance on Russian ships, but the publisher for 20,000 Leagues Under the Sea asked Verne to remove this for concerns about international diplomacy and the risk of getting his entire scifi collection banned from the Russian market. So Nemo is unspecified there because of RL meddling. There's still a bunch of secondary traces that Verne didn't expunge, like the guesses you mention, and the portrait of the Polish Thaddeus Kosciuszko being the first of the freedom fighters on Nemo's wall, hanging next to people like George Washington and Abraham Lincoln, with no Indians mentioned there.3. Thyrus is visibly Indic and he's marveling at how not racist Mathilde is. Like how in the first 20,000 Leagues Under the Sea book it was an intentional mystery what nationality Nemo was, so every character guesses where he's from, mostly guessing European countries. And when subsequent materiel revealed he was visibly Indian the whole time, all those guessers accidentally look like the most PC 1800's book characters ever.
The Mysterious Island was part reveal, part retcon. The timeline doesn't match up. Leagues happens in 1866-68 and Nemo is out on adventure with an active crew; Island happens in 1865-67 and Dakkar has been stuck there for many years and he's come there after being at sea long enough that his crew has died off.
Verne handwaves this by saying the "real" dates have been classified to avoid leaking military information.