Have Buddhas escaped samsara? Have Buddhas escaped samsara? Obviously there is the mainly Chinese term "non-abiding in nirvana". I'm interested in an answer from any tradition at all, and for enlightened non-Buddhas, too.

To be specific, I would like to know if when a Buddha dies they then suffer death, or whether their death is somehow something over and above the suffering of samsara.

I'm asking just because I think that's how I'd like the near eternal rounds of rebirth to end, perhaps with a little regret.

Cheers.
Regret requires aversion and ignorance. It's ignorance that makes one think that there's anything worth in Samsara to miss. Enlightened beings(Arahaths and Buddhas) have uprooted all defilements. So it's technically impossible for them to feel regret or sadness.