Edit: Just looked up your device: You are running on ARM64 (aarch64) so it will not be compatible with x86 architectures. Even though Python is not a compiled language, stuff like Qt is compiled for different architectures. Also, you don't mention if your app is compiled or Python based. So more info would help. You likely will need to cross-compile.
(Call this then the zeroeth mistake)
Well first mistake is putting it in a .deb.
- Most people don't know debs can be unzipped and repacked.
- Debs dependencies are specified in the control file. You need to be careful with this as one wrong move and apt et al. will be lost.
- "Linux App Store"? Man I must be old. I know about Flathub and AppImage Hub...
... which neatly segways me into the first piece of advice: Use an AppImage for release.
- You can dump all your dependencies and copy your venv into it and then use the app run script as an entry point.
- Some users appreciate not having to install apps, especially from newer developers.