They may still use discrete circuitry on their high end workstations, but I'm not sure. Korg embraced all-DSP synthesis early while their Japanese competitors (Roland, Yamaha, Akai) maxed out on sample playback and high polyphony. They have always had a narrow focus on synthesis, with minor incursions into the guitar utility/space, whereas Roland has a massive product catalog of electronic instruments (but a highly proprietary ethos) and Yamaha hasn't done anything in years (a pity, as they made great hardware sequencers. Akai is a special case as they basically own the market for hip-hop and its derivatives but are also unable to break out of it. I believe their gear runs on Linux, but like the other two their hardware/software stack is heavily locked down.
Regarding Yamaha and synthesizers I just wanted to mention that I consistently hear rave reviews of the Reface CS. I am more into vintage electric piano sounds than synths and currently own a Reface CP and the sounds on that are legit.
Akai has really been disappointing since they were purchased by inMusic brands. They have released a bunch of half baked products with serious bugs. (Looking at you, Akai Force).
You might also like this (though I don't know if it's using the R-Pi or is user-moddable): https://www.korg.com/us/products/dj/nts_2_pt/
They may still use discrete circuitry on their high end workstations, but I'm not sure. Korg embraced all-DSP synthesis early while their Japanese competitors (Roland, Yamaha, Akai) maxed out on sample playback and high polyphony. They have always had a narrow focus on synthesis, with minor incursions into the guitar utility/space, whereas Roland has a massive product catalog of electronic instruments (but a highly proprietary ethos) and Yamaha hasn't done anything in years (a pity, as they made great hardware sequencers. Akai is a special case as they basically own the market for hip-hop and its derivatives but are also unable to break out of it. I believe their gear runs on Linux, but like the other two their hardware/software stack is heavily locked down.