In QGIS 3.2 two new algorithms for segmentizing curved geometries have been added to Processing.
"Segmentize by maximum distance": The segmentization is performed by specifying the maximum allowed offset distance between the original curve and the segmentized representation.
"Segmentize by maximum angle": The segmentization is performed by specifying the maximum allowed radius angle between vertices on the straightened geometry (e.g the angle of the arc created from the original arc center to consective output vertices on the linearized geometry).