CMSAdminCookiesSameSiteNone still uses "Lax"

Hi.

We have some trouble with running the form builder in the admin app.

Our setup is a multi-domain environment, with admin and live app running on HTTPS.

We set CMSAdminCookiesSameSiteNone to true for both, the admin app in web.config and the live app in appsettings.json.

But, when trying to load the Form Builder from the admin app, we see the error message:

This page does not work properly as your browser may be blocking 3rd party cookies and/or the system may be incorrectly configured for a multi-domain environment. See our documentation for more information.

and the KenticoCookiePolicyCheck has this cookie:

KenticoCookiePolicyTest 
path    "/"
samesite    "Lax"
value   "413a9af1-9b38-43e9-810c-d333ff91556b"

which Firefox rejects with

Cookie “KenticoCookiePolicyTest” has been rejected because it is in a cross-site context and its “SameSite” is “Lax” or “Strict”.

The Form Builder also does not show up, there is this error:

InvalidVirtualContextException: Try reloading the administration interface. The user was not found in the JWT token, nor in the current virtual context URL.

    Kentico.Content.Web.Mvc.VirtualContextPrincipalRetriever.GetPrincipal(string jwtToken)
    Kentico.Content.Web.Mvc.VirtualContextRequestPrincipalRetriever.Retrieve(HttpRequest request)
    Kentico.Web.Mvc.AuthenticationHandler.HandleAuthenticateAsync()
    Microsoft.AspNetCore.Authentication.AuthenticationHandler<TOptions>.AuthenticateAsync()
    Microsoft.AspNetCore.Authentication.AuthenticationService.AuthenticateAsync(HttpContext     context, string scheme)
    Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
    Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
    Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
    Kentico.Content.Web.Mvc.ContentOutputMiddleware.InvokeAsync(HttpContext context)
    Kentico.Web.Mvc.KenticoRequestLocalizationMiddleware.InvokeAsync(HttpContext context)
    Kentico.Content.Web.Mvc.PageRedirectionContextMiddleware.InvokeAsync(HttpContext context)
    Kentico.Web.Mvc.KenticoRequestEventsMiddleware.InvokeAsync(HttpContext context)
    Microsoft.AspNetCore.Diagnostics.StatusCodePagesMiddleware.Invoke(HttpContext context)
    Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

What does this mean? How can we fix this?

Thanks!