I contacted Samsung tech support with this issue and they told me this was NOT a known issue and they had no plans to issue a software update to address it. I promptly exchanged my S(+ for another one (still in the 14 day window). My new S9+ has no problems reading the SD card. If you're in the 14 day window experiencing this problem, you should do an exchange. My guess is that when Samsung gets many S9's returned for SD issues, they'll realize they have a problem.
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