I was trying to find the ripple rejection spec for the MIC29302, but found a pre-Microchip MIC29302A datasheet: here It seems to be a slightly different version (low cost) of the chip for 20V operation. While it is a different chip, it would be from the same base design and can give some rough idea what to expect.
It is hard to read off the log scale. A bit of messing around with Excel graphing option, I got myself a semi-log graph.
After some image editing and fooling around with transparency and scaling, I superimposed the grid onto the graph.
The ripple rejection drop to about 5dB at around 250kHz. Above that, it is mostly the bulk decoupling cap doing most of the filtering work.
XL6009 Buck-Boost converter switches at 400kHz, the ripple rejection is ~15dB. What this means is that if the ripple at the LDO input is 10mV p-p, the amount of ripple at the output:
10mV * 10^(-15/20) = 1.77mV p-p
Chances are that the ripple from cheap Chinese modules could be pretty bad. They have a small LC filter using a small inductor and a MLCC. I don't know the extent of its performance until it arrives.
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