There's probably more blocks that rails cannot be placed on, but could by world generation, but we don't have time to find more of them.

Normally, rails cannot be placed on dirt paths as it's not a full block. However, if a mineshaft generates near a village, the rail(s) can generate(s) on the dirt path(s). Now, this is practically impossible in normal world because villages are on ground structures and mineshafts are underground structures, however this can be reproduced in a superflat world.

1.21.1
Seed: -9223332948529622761
World type: Superflat, modified version of Overworld preset: 79*minecraft:air,minecraft:bedrock;minecraft:plains
Coordinates: /execute in overworld run tp 136 16 348

Similar to MC-273441, this in theory can happen in the normal world, there're 2 ways this can happen, both are very very rare in the normal world and we can't find it yet.
1) (My way) A non-desert village somehow not only generates underground but also low enough to be in the levels of mineshafts spawning, then a mineshaft needs to spawn next to a village such that one of the rail in mineshaft spawn on a dirt path in village. Now, we're not sure if underground village is intended of not and we cannot find any open issues about underground village, the closest bug report we can find is MC-240953, however this doesn't really matter bc of the 2nd way.
2) (NguyenFranky's way) A non-desert village spawns on the boundary of a badlands biome, which then a surface mesa mineshaft spawn near it, which then a rail is placed on a dirt path. This way doesn't require an underground village and is much more simple than the 1st way.