> How come this is trying to install its own vendored dependencies, including executable binaries, instead of checking for what's already installed? That approach can lead to both security and performance issues.
I've been sympathetic to your viewpoint, and I can see why this kind of thing is becoming more common.
The idea that users can reliably supply their own vendor libs/execs for applications is a bit of a fantasy. Devs working on fixing issues caused by the user having a strange issue due to the version of Python or whatever that they have installed is largely a waste of time when the application can "simply" ship with the exact dependencies it expects. This is especially true when it comes to open source work. Dealing with weird edge cases because the user has a version of FFMPEG installed that, for whatever reason, is missing h264, is work that nobody asked for. Given that the audience of this kind of app is a general one (not specific at all to devs) then it doesn't make sense to require other system packages to be present; if things like Python and FFMPEG are not required and will be downloaded anyway as part of the app install process, then there's no point in not always doing that. If you think about it, it's hardly different from any other sort of software dependency. The dependencies are just relatively bigger.
Personally, I have no desire for my applications to use other executables on my system unless I request that they do so explicitly. I'm sympathetic to the idea from a mere efficiency perspective, especially when it comes to developer tooling. But a karaoke app? No offense, but why care? A Python interpreter will be anywhere between 50 and 200 megabytes. FFMPEG is even smaller, especially if you don't enable every single feature and codec. Compared to how ridiculously bloated your average basic mobile app is (without anything like a built in JIT), bundling a desktop application with something like Python provides a lot of power relative to the number of bytes added.