I’m having the same issue. Just upgraded from 2023.5 to 2023.6.3.
Custom elements do mostly work but not when accessing HA from Chrome desktop via my domain. Hard reload and clearing cookies did not help. However it works on all other browsers (+ mobile).
Just found out it also works on a different Chrome profile.
I am having a simular issue after installing 2024 6 3. None of my dashboards came up in ha app with custom element does not exist error. They all display correctly in chrome browser.
As another post suggested, I repeatedly cleared app cache and restarted. Eventually everything worked except custom element doesn*t exist dwains-dashboard-layout.
Everything works on browsers including Dwain’s and now everything in app except Dwain’s. No recent chages were made to any dashboard.
I haven’t got a clue. Would appreciate suggestion.
Wallace