Screen readers and other assistive technologies depend on lists being structured properly to keep users informed of content within the lists. The only content lists should contain should be within <li> elements. They can also contain script supporting elements (<script> and <template>).
How this Lighthouse audit fails
Lighthouse flags lists that contain content elements that shouldn't be in a list:

How to create correctly structured lists
Remove any elements in lists that don't belong there. Ordered and unordered lists must only contain <li>, <script> or <template> elements.
Valid lists must have parent elements (<ul> or <ol> elements) and child elements (<li> elements). Any other content elements are invalid.