@Puddin @Rook So i can tell you why it doesn't work, since i now tried it with Sideloadly!
There was an issue during installation: 0:
DeviceNotSupportedByThinning
This app is not compatible with this device.
This app specifies a value for UISupportedDevices in its Info.plist as:
[iPhone10,2, iPhone10,3, iPhone10,5, iPhone10,6,
iPhone11,2, iPhone11,4, iPhone11,6,
iPhone12,3, iPhone12,5,
iPhone13,1, iPhone13,2, iPhone13,3, iPhone13,4,
iPhone14,2, iPhone14,3, iPhone14,4, iPhone14,5, iPhone14,7, iPhone14,8,
iPhone15,2, iPhone15,3, iPhone15,4, iPhone15,5,
iPhone16,1, iPhone16,2,
iPhone8,2, iPhone9,2, iPhone9,4]
but none of the identifiers in this device's compatibility list are present in this app's supported devices.
This device is compatible with [iPhone18,2, iPhone17,2].
Means: My iPhone model is not listed in the Info.plist supported-device list.
Solution:
I fixed the install issue by editing the app’s Info.plist and removing the UISupportedDevices key, because the IPA was restricted to older iPhone model identifiers and my newer device was being rejected with DeviceNotSupportedByThinning; after repacking and signing the IPA again, it installed successfully.