Both are correct.  See https://www.grammarbook.com/homonyms/in-regards-to-with-regards-to.asp

However many people say “regarding”, especially when reading out *in re*in emails, letters , legal decisions, and so on.  Reading It aloud in Latin is felt by some to be pretentious if not elitist, especially these days.

Voragh

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From: tlhIngan-Hol <tlhingan-hol-bounces@lists.kli.org> On Behalf Of mayqel qunen'oS

You're a native American. In your everyday speech with your wife, friends, etc, do you say "with regard" or "with regards"?

('amerI'qa'nganna' SoH. qaStaHvIS Hoch jaj yIn, be'nallI'vaD juppu'lI'vaD latlh(pu')vaD joq bIjatlhtaHvIS, < with regard > bIjatlh'a'? pagh <with regards > bIjatlh'a'?)