I've been trying for the Australia-Hungary achievement without doing any glitches, gimmicks (like disabling certain DLC), or other unintended stuff and it's been brutal. Starting as an Australian tribe has to be the worst tech situation in the game. You go horde to be able to get out of the continent but the horde reform tree is short and you only get one estate -- not ideal when you're probably going to play somewhat tall at times.
It was roughly 60-70 years before I could get off the island after much speed 5ing. But the real zinger is that if you reform out of a horde into a monarchy, republic, or theocracy, you go BACK to you original tech group, of which there are ZERO other nations in the game. Since you have to dev for each institution and don't even start with Feudalism you are waaaaay behind the curve and since you're the only one with the tech group you don't get a neighbor bonus from being the same tech group. Just move the capital to get near countries for that neighbor bonus, you say? Nope, as soon as you move the capital out of Australia, Australia becomes a colony and you can't do the achievement. Sure, you could move out and later on do something where you release the colony, take back same provinces and move the capital, then retake the rest, but I think that really goes against the spirit of the achievement and it's still a huge pain.
So my option was to conquer land from another religion such that I could accept religious rebel demands (getting a different religion) and then turn into a different government (which only then switches the tech group). It's the early 1600s and I've just become up to date on tech. My plan to befriend the Ottomans to help take Hungary has failed because the Ottos are getting buttfucked. Austria is the Emperor, huge, has Russian as an ally, and has all the Hungarian land, so now I need to get super swole to even be able to take that. The mission tree for an Australian tribe offers no useful permanent military modifiers and I haven't been able to afford a military idea group. If I declared war right now, it'd be their 600k troops to my 170k. Ouch.
It's been hell and I probably won't finish until the 1700s at this point (currently 1638), even though I'm just barely the #1 great power.