I know you can get them sometimes from chests or NPCs, and the wiki lists some fixed spell tomes, but I'm looking for locations with randomized spell tomes, like you can find in a hidden room in the temple of Miraak.

Due to it being randomized loot, they can appear anywhere at random as part of normal random loot, there is no specific place that is random, it's always completely random due to it being random.

Random.

I'm talking about places where you can find randomized spell tomes OUTSIDE of containers.

not completely random. There are items in the creation kit that specify a particular kind of random item. There might for instance be on a table a random leveled potion. You wouldn't know what potion would appear but some potion would at that spot. The easiest way to find random spell tome locations would be to look in the creation kit. You could right click it and get a list of all locations that had that reference.

Fixed spell tome, always there - yes

Random spell tome, random chance - yes

Random spell tome, always there - no

Fixed spell tome, random chance - no

The places where you can find a random weapon, or potion etc. are a special form of container with a single item as content. The only "Dummy book" object can contain any book, which may randomly be a spell book, if that list is used.