To hide add to cart button in Event Widget, go to theme editior and click on Servv app. Then, click Custom CSS and add this code block:
{% style %}#svv-wgt-app .svv-event-card-item.list-layout-item .svv-purchase-controls-container .svv-add-to-cart-btn {display: none !important;}#svv-wgt-app .svv-event-card-item.grid-layout-item .svv-add-to-cart-btn {display: none !important;}{%endstyle%}