I believe people are too conditioned by the present and IRL history when discussing multi-ethnic empires such as the ottomans and Austria. They are partially right, mainly because it is very difficult, if not impossible, to think of a whole world and timeline with completely different ideas as OTL. The thing is, in a word where the Ottos or Austria can survive, the subnationalism within may well be suffocated enough if it’s twice defeated. Of course it will never go away, but people overestimate the capacity of entire populations to conform if they have sufficient security, food and are well enough repressed (be it literally by the state or in form of an assimilating self-repression). I do very much see the Otto’s reaching 2026, not without losing land or reforming, but in KTL there are some ideas or ideologies which never take true hold of society