What is the better version ? SDL or QT ?

[[Unknown]]

I don't know anything about that ppa itself, sorry. It's maintained by someone in the community, I'm a regular contributor to the main PPSSPP repo. So I can tell you about the code itself, but not that ppa.

There's no other Linux port, it's either SDL or Qt. Maybe "ppsspp" actually means both or something?

Native menus means like the "File", "Help", etc. menus native apps have on Linux. The Qt version has similar menus to the Windows version, which means you can change some options directly in the native menu.

All platforms (Windows, Android, Linux/Qt, Linux/SDL, etc.) have the options accessible within PPSSPP, and there's nothing exclusive to the native menus.

But Qt also offers a native file browser dialog to select files or folders, where in SDL you just have to browse to the folder. Basically, the Qt build has better integration with native KDE or GNOME features, which the SDL build doesn't. But outside the better integration, all the emulation code is exactly the same.

Again, the only difference when a game is actually playing is no one has done the work to enable Vulkan on Qt. It's possible, just no one has been interested enough to contribute to it and get it working.

-[Unknown]