https://www.politifact.com/factchecks/2019/nov/11/viral-image/no-evidence-449000-noncitizens-were-registered-vot/
Summary:
From 2016-17 449,404 were disqualified from jury duty for not being U.S. citizens. But that doesn’t mean that those rejected juror candidates were registered to vote. The DMV has a "motor voter" program that automatically registers eligible driver’s license applicants unless they opt out. Sometimes, people will inadvertently mark themselves down to register to vote and it’s possible that the lists courts receive from the DMV include these individuals. The California Secretary of State office then reviews the lists and cancels requests to register to vote from people who aren’t eligible. Therefor, the claim is false.