Hi @MrGormit_13
Please digest the information from @Lucas001. The simple way I can think of is to embed your Power App in Power Pages and allow your external to access it.
1. Integrate canvas apps into websites and other services. Link here
2. Adding an iframe in Power Pages. Link here
Bonus: Video from one of our MVPs. Link here
You need to change a few data security models in your Power App to achieve this.
Hope it helps.
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