Before TestFlight was a thing, you could self-sign your own apps (.ipa) and install them to local devices through iTunes over a USB cable connected to the device. The developer signing certificate for this was/is free, included when you sign up for the free version of Apple Developer account.
Nowadays it looks like you can still do this directly from Xcode. See section: “Connect real devices to your Mac”
*The mention of Apple Developer Program in the bullet points of this section is an “if” and is optional. It’s not required for testing apps on local devices.
Before TestFlight was a thing, you could self-sign your own apps (.ipa) and install them to local devices through iTunes over a USB cable connected to the device. The developer signing certificate for this was/is free, included when you sign up for the free version of Apple Developer account.
Nowadays it looks like you can still do this directly from Xcode. See section: “Connect real devices to your Mac”
https://developer.apple.com/documentation/xcode/running-your-app-in-simulator-or-on-a-device
*The mention of Apple Developer Program in the bullet points of this section is an “if” and is optional. It’s not required for testing apps on local devices.