With my upgrade of HA core from 2022.5.0 to 2022.5.1 the frontend of the Zigbee2MQTT addon is no longer reachable when clicking on the ingress link in the sidebar.
I suspect it is not the upgrade of HA core from 2022.5.0 to 2022.5.1 (z2m works perfectly here) but the latest update to z2m to v1.25.0-1 and then to v1.25.1-1. Look here and here to learn about the Breaking Changes of the z2m add-on.
I reinstalled the addon today, and it worked right away with no changes in the GUI configuration (and my existing config files). Thank you!