deep-focus-trap (npm): A focus trap library that pierces that shadow dom. So you can use it with native web components. Deep Focus Trap  is a lightweight library written in vanilla js with only one dependency (that is tree-shakable if not in use).
Keywords: focus|accessibility|trap|capture|keyboard|modal|ADA|compliance|ShadowDOM|Shadow|DOM|Web Components|tabbable|javascript|JS|A11Y|deep|lit|lit-element|light-dom-elements|shadow-dom