So technically we have the Karamanids and Mamluks against the Jalayrids. Then I got a couple more questions: are the Karamanids and Timurids enemies? Can the Byzantines still collapse, even without the Ottomans? More importantly, can the Karamanids succeed or fail in conquering the Balkans?
1. The timurid where only really a big deal for about three years before their borders receded after Timurs death and he isn't gonna live much longer after the start of the interregnum so they didn't have time to really make friends or enemies.
2. They had already collapsed by then and where living on borrowed time well before Timurs appearance.
3. My guess is barring some out of the ballpark luck they won't succeed in the Balkans long term, the Karaminids don't have as good a military system as the Ottomans did.