Remove Qty Box from mini cart and the page of checkout page

Copy the following file:

/vendor/magento/module-checkout/view/frontend/web/template/minicart/item/default.html

to your theme:

app/design/frontend/Vendor/Theme/Magento_Checkout/template/minicart/item/default.html

And remove the qty code like below:

<!-- /** * Copyright © Magento, Inc. All rights reserved. * See COPYING.txt for license details. */ --> <li class="item product product-item" data-role="product-item"> <div class="product"> <!-- ko if: product_has_url --> <a data-bind="attr: {href: product_url, title: product_name}" tabindex="-1" class="product-item-photo"> <!-- ko foreach: $parent.getRegion('itemImage') --> <!-- ko template: {name: getTemplate(), data: item.product_image} --><!-- /ko --> <!-- /ko --> </a> <!-- /ko --> <!-- ko ifnot: product_has_url --> <span class="product-item-photo"> <!-- ko foreach: $parent.getRegion('itemImage') --> <!-- ko template: {name: getTemplate(), data: item.product_image} --><!-- /ko --> <!-- /ko --> </span> <!-- /ko --> <div class="product-item-details"> <strong class="product-item-name"> <!-- ko if: product_has_url --> <a data-bind="attr: {href: product_url}, text: product_name"></a> <!-- /ko --> <!-- ko ifnot: product_has_url --> <!-- ko text: product_name --><!-- /ko --> <!-- /ko --> </strong> <!-- ko if: options.length --> <div class="product options" data-mage-init='{"collapsible":{"openedState": "active", "saveState": false}}'> <span data-role="title" class="toggle"><!-- ko i18n: 'See Details' --><!-- /ko --></span> <div data-role="content" class="content"> <strong class="subtitle"><!-- ko i18n: 'Options Details' --><!-- /ko --></strong> <dl class="product options list"> <!-- ko foreach: { data: options, as: 'option' } --> <dt class="label"><!-- ko text: option.label --><!-- /ko --></dt> <dd class="values"> <!-- ko if: Array.isArray(option.value) --> <span data-bind="html: option.value.join('<br>')"></span> <!-- /ko --> <!-- ko ifnot: Array.isArray(option.value) --> <span data-bind="html: option.value"></span> <!-- /ko --> </dd> <!-- /ko --> </dl> </div> </div> <!-- /ko --> <div class="product-item-pricing"> <!-- ko if: canApplyMsrp --> <div class="details-map"> <span class="label" data-bind="i18n: 'Price'"></span> <span class="value" data-bind="i18n: 'See price before order confirmation.'"></span> </div> <!-- /ko --> <!-- ko ifnot: canApplyMsrp --> <!-- ko foreach: $parent.getRegion('priceSidebar') --> <!-- ko template: {name: getTemplate(), data: item.product_price, as: 'price'} --><!-- /ko --> <!-- /ko --> <!-- /ko --> </div> <div class="product actions"> <!-- ko if: is_visible_in_site_visibility --> <div class="primary"> <a data-bind="attr: {href: configure_url, title: $t('Edit item')}" class="action edit"> <span data-bind="i18n: 'Edit'"></span> </a> </div> <!-- /ko --> <div class="secondary"> <a href="#" data-bind="attr: {'data-cart-item': item_id, title: $t('Remove item')}" class="action delete"> <span data-bind="i18n: 'Remove'"></span> </a> </div> </div> </div> </div> </li> 

Now run static-content deploy and check.

For Checkout Cart Page:

Copy the file

/vendor/magento/module-checkout/view/frontend/templates/cart/form.phtml

to your theme:

app/design/frontend/Vendor/Theme/Magento_Checkout/templates/cart/form.phtml

and remove the Qty from table head.

Now copy the file

/vendor/magento/module-checkout/view/frontend/templates/cart/item/default.phtml

to your theme:

app/design/frontend/Vendor/Theme/Magento_Checkout/templates/cart/item/default.phtml

And remove the Qty block.

Refresh the cache and check.