Hi @Anonymous ,
This is a broad topic and requires Microsoft's involvement. You are right, few things we are not aware of it. They are.
1. Region where the App is hosted
2. Switch to HTTP/2 to increase the performance load.
There are various factor can slow down it may be due to latency, network issues, or other extensions in client-side which are preventing the portal to load fast.
When the powerapps portal is provisioned Microsoft should allow us to choose the nearest region.
Workaround:
1. Try fiddler trace to see what is causing the slowness for the first time.
2. Make sure you allow cookies on your client-side.
3. Use the lighthouse tool to check your performance and other speed-related issues. This is a great tool that will allow you to think aloud and focus on improving your performance of the portal. URL: https://web.dev/measure/
Hope it helps.
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