The new security concept denies requests to sensitive xampp folders from all IPs but localhost/127.0.0.1.
localhost is not equal to your public IP or private LAN IP! localhost should work.
If you want to access phpmyadmin from other IPs, you had to remove the phpmyadmin folder from the secure List in the httpd-xampp.conf file and give the phpmyadmin directory another access directive (
but thats not recommend unless there is no other way!)