Now this
https://www.alternatehistory.com/discussion/showthread.php?p=4754798&highlight=poland#post4754798 is the biggest non-joke Poland I've seen on the board.
I find it a bit dubious, but I suppose if Timur hadn't screwed over the Golden Horde they might have won the 15th century match with Moscow and kept north Russia weak and fragmented a bit longer, giving a more centralized Poland-Lithuania a chance to conquer and Catholicize/Pole-ize the fairly underpopulated south, perhaps even to the Caucuses (although this probably also requires no Ottoman empire: perhaps Timur leaves the Golden Horde alone and concentrates on conquering the Ottomans?). It seems however geographically unlikely that they're going to beat the Great Russians into Siberia.
And Poland and Hungary were united dynastically a while: a few sperm go the other way, and perhaps it would be Poland rather than Austria that spends a hundred and fifty years holding onto a melon rind of Hungary and fighting the Ottomans. A Balkans-involved Poland is interesting too, although we are once again moving to multi-national federation rather than nation-state. Poland on the Black, Adriatic and Baltic seas all at once? Admittedly, Poland-Lithuania-Hungary doesn't sound particularly stable...
Bruce