You might be OK with just some filtering on the analog power pins of the microcontroller. I typically just use a small SMD “ferrite bead” type inductor and capacitors. You’d want to do this anyway, since digital circuits will add noise of their own.
You also should use other features, such as a ground plane and segregating the sensitive analog section from the sources of noise.
After saying that, adding an LDO post-regulator can be an easy way of greatly reducing power supply ripple. Set your switchmode regulator a little above the LDO regulator voltage (you don’t want to waste too much power).