So im trying to apply a pattern along path with the LPE.

My path is a 500x500px circle.
As soon as i select the LPE, the circle is deformed.

When i apply the pattern, the circle is still deformed, meaning my final image is not a perfect circle.
Is this a bug ?

To me this looks like an imprecision when doing the conversion to a path (which is done internally, still keeping the attributes of the circle, but in a separate set of properties). I tried raising Inkscape's precision, but it didn't change anything, only the length of the numbers, but not the appearance of the circle.

Can't tell you if it's a bug or how much imprecision is to be expected, but what helps as a workaround is to convert to path, select all nodes and add a few with the + button in the top left. Only then apply the path effect.

Thanks Moini !