Similar situation to Israel. Israel won’t officially confirm or deny. But is believed to almost certainly have them.
Taiwan officially denies having them but is know to have had secret development programs in the past which were supposedly shut down after they were discovered. You would have to be pretty naive to believe that they didn’t secretly reactivate the program, especially when you consider the threat posed by the mainland. That’s to say nothing of rumours and leaks about their capability.
OK, so how do you KNOW Israel has nukes when they won’t officially confirm or deny? Obviously from other sources.
We KNOW Taiwan had a nuke program because they admitted to it and agreed to terminate it. However, it has been rumoured that they either secretly continued the program or reactivated it and now have nuke capability. Given their demonstrated willingness to secretly pursue nukes in the past and the strategic imperative.
I would rate Israel as 99%-100% likely to have nukes and Taiwan as 95%-98% likely i.e. almost certain.