Is there an equivalent to $A.get("$Browser.formFactor") in LWC?
As of today, there is a lwc module that you can import to get it:
https://developer.salesforce.com/docs/component-library/documentation/lwc/lwc.create_client_form_factor
Hope that helps
Edit Dec. 2020: Now available via @salesforce/client/formFactor
import
No there is no equivalent of $Browser.formFactor
Aura global value provider in LWC. The addition of an equivalent is under discussion.
For now, you can use CSS media queries and Element.getBoundingClientRect to make component adapt to the space available on the screen.