Java I don't think is a good option for Linux - as there are just to many different Java , Oracle Java, IBM Java, openjdk - each in different versions. At work we have quite often problems with different application which are written for one specific Java and the customer uses another .
Mono XWT I do not know much about

Mono works on Linux but I'm not sure how well it is maintained . To my knowledge its only maintained by a small Team and I'm not sure where their focus is. .net is still very microsoftcentric

try reverting to the pöayer before Persia - eventually you need to revert a whole turn

Kal MooRe - consider joining the civilisationleague - we play via GMR

https://civilizationleague.org/

feel free to join and challenge players.

you know there a lot of possibilities to cheat . In game and in Life. It just depends on trust that you do not do it. Not everything can be technicaly prevented.

not sure as I'm not a developer but I can easily be a betatester.

Yes there is - Qt is duallicensed , commercial in case and LGPL to my knowledge . For Example the Plasma Desktop (KDE) is based on Qt . But I'm afraid I'm not a Lawyer so I don't know if you can use the LGPL Version .
I would be very happy with a Qt Version

btw. its Qt - pronoucend cute (afaik) - i think QT would be Quicktime
but this is just a nitpick :D

normally should not be an issue . I would raise the issue with support

had that also sometimes its a good workaround

I can't play any of my games either . But I wait for the Oracle Version to try again - any news on that?