The PS4 scene has made significant progress since SpecterDev released the PS4 4.05 Jailbreak at the end of 2017. Although PS4s running 4.05 are getting hard to find at a reasonable price, they now allow a variety of features, from custom themes to Linux, and including, yes, Piracy.

Here’s a quick list of what you can do so far on a hacked PS4 4.05, in no specific order:
Linux on PS4

Linux on the PS4 was a thing on firmware 1.76 (formerly the only hacked firmware), and that has been ported to firmware 4.05. Multiple distributions are circulating on scene sites, and, although the port has its limitations, it’s always cool to run Linux on yet one more device.

Run your PS4 as an FTP Server

You can use your PS4 as a local FTP Server. Today, this is mostly useful for people who want to retrieve and analyze files from their PS4, but this could lead to more in the future. The PS4 Exploit Host tool has everything you need to get started (that tool is useful for pretty much everything mentioned on this page), or you might want to check this (older) tutorial: How to run an FTP Server and access your PS4’s files (with full root access).

Registry edits, debug settings, and more customization

You can tweak your console’s internal parameters, if you’re not too afraid of messing it up. Oct0xor’s PS4 Registry Editor, as well as the debug settings payload will help you do that.

PS4 Custom Themes

You can create your own PS4 themes and install them as a package thanks to PS4Hen. Tools such as PS4 Theme Editor are here to simplify the process, and you can look for more themes in our thread here.

PS2 Isos

Hackers have cracked the code to running PS2 games on the PS4. The system supports not only the PS2 Classics games officially supported by Sony, but also more isos. A compatibility list is available on ps4devwiki.

PS4 Piracy

I have to mention it here as I know it will be the main reason most people will try to get their hands on a PS4 4.05. PS4 piracy is a thing on firmware 4.05. Games such as Minecraft and Uncharted 4 have been released by Warez sites, and confirm to run on hacked PS4 4.05, through the PS4Hen payload. Please don’t ask on this site where or how to get these games.

PS4 Homebrew?

In theory we should be able to start creating homebrew for the PS4, and release them as pkg files (just like official games). So far though, the scene has been a bit slow on that aspect (most “homebrew” code released so far has been binary payloads for the exploit). In theory all you need to get started is a 4.05 compatible PS4 SDK, but maybe what the scene needs is a good tutorial.
Did I miss any cool feature of hacked PS4s? Please let me know in the comments!