I'm not sure, but I think there is a way. I don't remember what it was though.

Now, you made me curious?!

There definitely is because in my game AI Maya reformed their religion by 600, which somehow made them both lose their Native government (which lets them literally build stuff like Storehouses ahead of intended) and also somehow qualify for spawning Organized Religion

Right now I can only "reform" to a tribal government, which would made me lose my whole kingdom, except the capital region.
The Maya might have received Organized Religion, because of a Province with a temple; this gives an incredible Boost!

That would make sense if it was solely the Religion Institution, but they've built Storehouses and actual Castles in their provinces, which makes me think they've fully gone to a reformed Feudal nation

Hmmm, but which neighbour could have made this reform possible about 600?

No clue, but they're continuing to construct storehouses and castles and now ports, not to mention they have spawn institutions

And you're sure, this happened around 600? Cause I'm 585 right now!^^

By the way: Are you plaing IronMan? Otherwise you could do me a huge favor and switch to the Maya via console command and tell me to which government they switched exactly...

Yeah it happened around 600, I can see them since I'm playing Iroquois. I tag switched to them and it shows that they have not reformed their religion and therefore no government reforms, but they have heirs and can construct things like storehouses. Their government is marked as Great League (which says it doesn't have a monarchy), so I have no clue how they're able to freely construct this stuff or get these institutions

Thx for your afford!
By the way: I'm fighting the Iroquis as Maya, really tough warriors!

I finally managed to do the reform to monarchy at about 725 by coincidence. After fighting the creek, I forced them to release a nation, which founded a mixture of some feudalistic tribe?!? This way I had a fitting neighbour, strange?!

Yeah, this also is a problem for Hellenic nations, in a different way. Someone decided that apparently you need a flat number of Christian provinces to reform a Hellenic nation. 20 provinces is no problem for the Roman Empire, but if you're playing a custom nation or manage to last long as a small Hellenic nation, then you're screwed.

There being no [reliable] way to reform is an issue. Maybe if we ever get new mission trees for the new world we could get something to fix that issue. It doesn't need to be easy but requiring 100 loyalty in an estate might work. Part of the problem is you can't reform off a primitive nation so in the current version even if you border a monarchy with an innovation you're stuck.

IE: mission requires 100 loyalty in at least 1 estate -> unlocks a decision -> decision triggers an event -> 100 noble = monarchy, 100 burgers = republic, 100 church = theocracy, 4th option to back out if selected by mistake -> picking option 1, 2, or 3 lets you click the reform religion option without bordering anything.