Yes, you can. You just need to sign it appropriately. Also, there's been multiple jailbreaks since iPhone 5.
Having to re-sign one’s apps every seven days (or pay $99/yr) barely counts, IMO; but yes, jailbreaking is easier than ever on any iPhone s as recent as the X/8.
Take a look at AltStore.io. A workaround for sure, but definitely simplifies the process of signing and sideloading apps without jailbreaking.