It's not possible to run it in the other way than a mousedown, but there is a workaround which will do the job for most cases:

import React, { useEffect, useRef } from 'react';
import { MDBRipple } from 'mdb-react-ui-kit';

export default function App() {
  const rippleRef = useRef(null);
  useEffect(() => {
    document.addEventListener('keydown', (e) => {
      const mouseDownEvent = new MouseEvent('mousedown', {
        bubbles: true,
        clientX: rippleRef.current?.clientWidth / 2,
        clientY: rippleRef.current?.clientHeight / 2,
      });
      rippleRef.current?.dispatchEvent(mouseDownEvent);
    });
  }, []);

  return (
    <MDBRipple ref={rippleRef} rippleTag='a' href='/'>
      <img alt='example' className='img-fluid rounded' src='https://mdbootstrap.com/img/new/standard/city/043.webp' />
    </MDBRipple>
  );
}

Since mousedown does not trigger submit or redirect when a link is targeted, I think it shouldn't have any unexpected impact on your app, and can be used safely.