LDO selection in low noise amplifier application
You can start by looking at the noise spectrum of the LDO and the PSRR (power supply rejection ratio) of the op-amp over that spectrum. It's not unusual to add some passive filtering on the supplies (R+C or ferrite bead + C) for sensitive parts or a capacitance multiplier so even a relatively noisy source may not be an issue. The IC makers would like to sell you a boutique part, of course, so they are not an unbiased source of information.