After delisting of the shares of Myriad Group AG you may still buy and sell shares of the company according to Swiss law and the articles of incorporation.
If you as a Myriad shareholder wish to sell shares, in principle it falls to you to find a buyer of the shares and to determine the share price.
In order to facilitate the buying and selling of Myriad shares, the company appointed BZ Bank Aktiengesellschaft to engage in over-the-counter trading of the Myriad Shares following the delisting of the Myriad Shares.
For over-the-counter trading, several Swiss financial institutions offer specific platforms of their own:
Lienhardt & Partner Privatbank Zürich AG: https://www.lienhardt.ch/private-banking/ausserboerslicher-handel/
Please contact your bank for further information on the over-the-counter trading of Myriad shares.