There is an entire level of geopolitics in the situation involving the UOC-MP, which is an arm of the Moscow Patriarchate in Ukraine, that is often either neglected or ignored in any discussion relating to the current situation in Ukraine with respect to Orthodoxy.
This goes back a few hundred years and it does involve Orthodox canonical law, to be sure.
The geopolitics have to do with how Church and State have cooperated with one another, especiallly within the Russian empire. This situation continues to exist today in Russia where the MP is little more than a department of the Russian government which gives a spiritual rubber stamp to what the state under Putin does to further its own, rather anti-Christian, goals and objectives.
The issue of authority within Orthodoxy is a convoluted one. It appears, at the outset, to define itself in terms of what the Catholic Church is not and that is always a bad way to do canonical law, just like it is a bad thing for Orthodoxy to define itself in terms of an antithesis to Catholicism.
This has lead to a kind of idealized, non-entity in terms of a nostalgia for a time when the Byzantine Emperor called together Ecumenical Councils as the ultimate authority for deciding matters of faith and discipline to a praxis involving, for example, the Moscow Patriarchate acting even more "papal" than the Vatican across a number of respects.
In the case of Ukrainian Orthodoxy, it was not simply the EP that reviewed the canonical history of Kyiv's Apostolic tradition being usurped by the Tsarist empire and came to the conclusion that Kyiv was and still is what it always has been with the right to ecclesial autocephaly. The people of Ukraine have evolved as such and as a Church to the point that they themselves wanted autocephaly and separation from the vice-grip of colonial Orthodox Russia.
For Ukrainians especially, the current war with its atrocities committed against them by "Orthodox Russia" has been an eye opener, once and for all. For them, there is nothing "Orthodox Christian" about Putin or his forces. He and they are rather "servants of Satan" as the Russian services to its New Martyrs and Confessors would have it and over a thousand formerly MP parishes have moved over to the OCU in the last six months with more to come.
Church and State are intertwined. I see that you use the oft-repeated "ethnic jurisdictions." In fact, that is an American construct which is, in fact, a false one. Even the OCA is little more than the "Russian Orthodox Church" in English transllation, something that became more than evident to me in conversations with OCA priests in the last ten years.
There is a moral crisis, moreover, within Orthodoxy today that my Orthodox friends simply hope will go away by itself. It won't, unfortunately. Orthodoxy in certain contexts has allowed itself to be the rubber stamp it has become.
For saying what I have said here, I know I will be chided by EC members voicing complaints by Orthodox members, essentially to tell me as an EC I have no right to say these things. But if so, rather than engage in open debate the choice will be made to shut it down, the issues here will not go away by themselves. The Church of Christ deserves better than that. It is not simply a beautiful series of services, colourful vestments and singing with gorgeous icons. There is more that is expected from us all by our Lord.