Exhibit 23(a)

Consent of Independent Registered Public Accounting Firm

MillerKnoll Retirement Plan

Zeeland, Michigan

We hereby consent to the incorporation by reference in Registration Statement No. 333-258170 on Form S-8 of MillerKnoll, Inc. our report dated June 29, 2026 appearing in the Annual Report on Form 11-K of the MillerKnoll Retirement Plan for the year ended December 31, 2025.

/s/ McConnell & Jones LLP

Houston, Texas

June 29, 2026