I think the Ottomans would be best served in gaining sheer land by ignoring Hungary once they dislodge them north of the Danube plus establish either vassals or military provinces akin to OTL's Bosnia Elayet in Transylvania/The Danubian Provinces, Vojvodina, Bosnia + Slavonia, Croatia Proper and the Crimea leaving them in undisputed control of the Danube and the Sava. Leaving those areas as military provinces while leaving a weak but not dependent Hungary north of the Danube makes the Ottomans' European flank more secure. And they can ideally mirror OTL Bosnia's religious history in some form giving the Ottomans more Muslims in the Balkans should they eventually lose control of these territories but keep their core in the Southern Balkans.
From there the Ottomans would IMO be best served in securing the title of Caliphate as decisively as possible. This means annexing Persia and the Gulf, establishing tributaries in Yemen(the mountainous highlands aren't worth fighting for IMO), northern Sudan, East Africa/Madagascar, and tightening their reigns over North Africa. Ideal strategic targets to gun for are Malta, Hormuz, and Zanzibar. To go along with this naval initiative would be direct attempts to stunt European adventures east of the Cape; stunt but not shut down. This gives the Ottomans some amount of leeway in playing off their military adventures in the Indian Ocean as pious Muslim initiatives while building up to an eventual ideology of pan-Islamism later on, whereas if they'd shut them down completely there'd be zero inkling of truth to this idea.
To meet the OP's challenge, you absolutely have to have the Ottomans take control of Australia for the sheer amounts of land that it adds to their sum total. And to go along with these a loose suzerainty over key Muslim regions under European siege, such as Aceh, the southern Philippines, Java, Malacca, etc. Because this theoretical Ottoman state focused their resources on the Indian Ocean and the Mediterranean instead of Central European adventures, let's say that they, not the Dutch are the ones to tear Portugal's empire asunder. This is the window where you can have the Ottomans come into control of strategic locations such as Hormuz, Muscat, Zanzibar, and Malacca/Singapore in some sort of analogue war during the Dutch War of Independence where the Ottomans come in like vultures. This is also where they could hop into seize the Philippines and Malta. If you really want to go for the gold medal, Gibraltar to unleash Maghrebi piracy on the Caribbean and Sevilla.
Fastforward a couple hundred years to the start of the industrial revolution and the Ottomans are in about the same position of dominance in the Indian Ocean that Britain found itself in at the end of the Napoleonic Wars except there's no one to give colonies back to. Definitely not leading the charge to industrialization but their stronger commercial links and greater involvement in trade and shipping means that they're going to adapt FAR better to industrialization and can hold their own. Fast forward another century to some ATL Scramble and the Ottomans are the 800 pound gorilla in the room as they've got East Africa, North Africa, and the Sahara on lockdown and have the Sahelian Muslim states in their pocket. While European states are fighting over mostly non-Muslim territories such as the West African coast and the Congo, the Ottomans' soft vassalage system used in Indonesia and later the Pacific has most of Europe by the balls. Between control of the Suez Canal, the Straights of Malacca, and almost all of the Indian Ocean's trade routes no European state that values trade with Asia is willing to push too aggressively on Ottoman vassals along the Niger River and the Sahelian band. Everything north between the Maghreb and the Sahel is indisputably Ottoman, no other power has any influence or means to push for land here.
Fast forward 20 years and the monopoly on oil, the demographics, and the pan-Islamist ideology being blasted by mass media has turned the Ottomans into a superpower bordering on a hyperpower in the Old World(presuming that a USA analogue arises and holds strong over the New World, otherwise nope, the Ottomans are an outright hyperpower).
This is about the theoretical peak for Ottoman expansion IMO. Exactly what lands they have or to what extent it's 'Ottoman', eh, that's all for someone more invested than me to debate. What I think the best bet for this to transpire would be an early shift in priorities from Europe to the Middle East for the Ottomans. Avoiding the Ottoman Interregnum is a good start and gives them a 50 year headstart, but I prefer a more ambitious hypothetical, where the Ottomans goad the Timurids into the same war as OTL but do so purposefully and rout them/slay Timur. This leaves an incredible power vacuum in the Middle East that they can ride all the way to Persia(IMO). This shifts almost all Ottoman attention away from the Balkans and butterflies the rise of Shia Islam in Iran. The Ottomans will be preoccupied with these adventures in the Middle East for close to the same amount of time as they spent in the interregnum if not longer and will come out with a radically altered set of priorities. This may even lead to the Persification of the Ottoman state and see them viewed by Europe as the second coming of the Achemaenid Persian Empire. And with that shift in character comes the permanent shifting of mentality and goals from a successor of Rome to a successor of Persia or even a successor of both. But whatever minimizes the attractiveness of marching into Vienna and defeating the HRE or marching into the Papacy and subjugating more Roman institutions that are more trouble than they're worth, the better.