You can check for any remaining official carrier or regional updates using these methods:
Communities on XDA Developers have ported Android 11, 12, and even 13 to the S4. Downloading LineageOS 18.1 or Pixel Experience for the S4 means downloading a 500MB zip file that contains a complete, modern operating system designed for a device Samsung abandoned eight years prior. The deep essay on this is one of optimization versus compatibility. These ROMs strip out Samsung’s heavy TouchWiz framework, replacing it with lightweight AOSP (Android Open Source Project) code. They use custom kernels to manage the old eMMC storage and CPU governors. samsung s4 software update download
For the average user, the only safe "download" is checking for updates directly on the phone or using Samsung Smart Switch. Do not download firmware files from unverified websites, as they often contain malware. You can check for any remaining official carrier