Domain attribute and SameSite attributes are independent of each other. Domain attribute defines the host to which the cookie will be sent. SameSite attribute allows servers to assert that a cookie ought not to be sent along with cross-site requests. SameSite attribute should be configurable independently of Domain attribute.
According to the specification, if server sends set-cookie header without SameSite attribute,
SameSite's default value is "Lax" (previously this was "None". It seems changed.).
Domain attribute and SameSite attributes are independent of each other. Domain attribute defines the host to which the cookie will be sent. SameSite attribute allows servers to assert that a cookie ought not to be sent along with cross-site requests. SameSite attribute should be configurable independently of Domain attribute.
https://www.rfc-editor.org/rfc/rfc6265#section-4.1.2.3
According to the specification, if server sends set-cookie header without SameSite attribute, SameSite's default value is "Lax" (previously this was "None". It seems changed.).
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie/SameSite
Note
This is breaking changes.