Faced with issue, when browser can't send cookies to different domain during ajax call, even
SameSite cookie attribute set to none, secure attribute set to true
withCredentials ajax param set to true
So, looks like we faced with Third-Party Cookie Blocking policy, that already enabled by default in Safari and will be enabled in nearest future in Chrome/FF/etc.
In case of Safari it called Intelligent Tracking Prevention (ITP)
You can find few options how to resolve it here : https://webkit.org/blog/10218/full-third-party-cookie-blocking-and-more/
But... seems like except Oauth redirects and iframe options, there are no any cross-browser ways for Ajax call?
Maybe someone has any solutions or workarounds, guys?