Surge XT is arguably the most powerful free synth on the planet. While it doesn't have the Trinity's specific PCM waveforms, it features a massive library of wavetables and "scene" layering that mimics the Trinity's combi mode.
Before we list alternatives, we must address the elephant in the room. Korg does not currently offer a Trinity VST. They have famously released software versions of the (Korg Collection M1) and the Wavestation , but the Trinity remains absent from their software roster. korg trinity vst free
This is a fantastic free emulation of the Korg PS-3100. While it's an older analog model rather than the digital Trinity, it captures that "vintage Korg" character perfectly. KORG Software Trials: Surge XT is arguably the most powerful free