The Delaware Court of Chancery in Manti Holdings, LLC v. Authentix Acquisition Co., Inc., C.A. No. 2017-0887-SG, memo. op. (Del. Ch. Aug 14, 2019), found that stockholders contractually waived their right to seek appraisal.
K&L Gates discusses the decision in Waiver Of Appraisal Rights In A Stockholder Agreement Is Enforceable Under Delaware Law.