If you are worried about security, Sideloadly is not a "site" that hosts apps, but a tool that allows you to "sideload" an IPA file you found elsewhere.
Here are some popular websites for downloading cracked and portable iOS apps for iPhone: best sites to download crack portableed ios apps iphone
Software piracy is a violation of copyright law in virtually every country. While individual users are rarely prosecuted, downloading and distributing cracked software remains illegal and can result in fines. If you are worried about security, Sideloadly is
use stolen or leaked enterprise certificates to host apps. While convenient, Apple frequently revokes these certificates, causing all downloaded apps to stop working (crashing on launch) until the site finds a new certificate. IPA Repositories: Communities like Decrypt.day use stolen or leaked enterprise certificates to host apps
A: No. All of the sites and tools listed above (except Cydia) work without jailbreaking. However, the best experience (permanent apps) requires a jailbreak or an old iOS version compatible with TrollStore.