Taiwan is composed of the refugee losers of the Chinese civil war. That gives them zero legitimacy to continue as anything but a breakaway state occupying a formerly Chinese province.
By this logic China should be returned to the winners of the Opium Wars [1]. No countries for losers! (To say nothing of the CCP’s inaction against Imperial Japan in WWII [2].)
Anyone can come up with reasons for stealing stuff based on decades, centuries or millennia-old gripes. What matters is where the people alive today live and how they identify. For good reason, the Taiwanese have been drifting away from China since Xi.
[1] https://en.m.wikipedia.org/wiki/First_Opium_War
[2] https://thediplomat.com/2014/09/the-ccp-didnt-fight-imperial...
No. Similar to how the Han Chinese don’t have one to Tibet (and other parts of modern-day China).
Practically all land touched by humans has multiple verifiable historical claims to it. The further back we go, the more there are and the more ambiguous they become. The only thing we can say with certainty is who is there today. Every other path means violence and is honestly a bit stupid.