Hi all 
I strongly advise against using the core auth in any frontend related work. There is no guarantee it will continue to work over time, as it is strictly only intended (and maintained) for backoffice access.
I wrote a blog post about this back in February, outlining an alternative and more robust solution to this challenge. You’ll find it right here: https://kjac.dev/posts/using-umb_ucontext-with-umbraco-14-plus/