Using 3rd party web components in LWC is not possible per this
https://developer.salesforce.com/docs/component-library/documentation/lwc/lwc.security_locker_custom_elements
Third-Party Web Components
To prevent security risks, you can’t use third-party web components on the Salesforce platform.
Web components are custom elements. To define a custom element, you
must use the customElements.define API. However, this API is global,
and allows you to globally register a component name. Registering a
name globally is a security risk because an attacker could register
any name and take over the page. Lightning Locker’s SecureWindow
wrapper blocks the customElements methods that create custom web
components.
The SecureWindow wrapper list in the Locker API Viewer tool shows that
customElements is not supported.
Created the idea for the same https://success.salesforce.com/ideaView?id=0873A000000PcvhQAC
Upvote the idea if you think having 3rd party web components in LWC is a good idea.
Note: Using react in LWC worked because it was not defining any web component.
import
of the Material library. However, that doesn't stop you from saving the CSS libraries as static resources and then reproducing what is on the web tab in this demo material-components.github.io/material-components-web-catalog/#/…