I have a machine with a xeon phi card, and while it is possible to give it work to do, it is in no way simple – it runs its own operating system, a flavor of linux, and you have to compile your code to run on it, since it is a different architecture, similar to how apple silicon is a different architecture and requires code to be compiled specifically for it.
beyond this, it is not just that you need to compile your code for this architecture, but you need to have a problem which is amenable to being coded to leverage the particular type of parallelism (vector) provided by the card – I was able to get a renderer to compile for it, which involved a lot of work to get the renderer’s third party libraries to also compile for it, but without changing how the renderer itself worked (and it was well able to use all cores), it proved to perform on the card on par with how it did on the core i7-4771 that was running the host machine.
in other words, the code was not aware of the degree & type of parallelism provided by the card, and so was not able to leverage it, and just ran how one might expect on a 57-core machine with non-hyperthreaded cores derived from the original p45 pentium design, running at barely over 1ghz.
besides all this, xeon phi is now a quite long deprecated technology, even the later standalone knight’s landing cpu versions which were capable of being installed on the motherboard as the sole cpu (being a hardware junkie, I have one of these as well).