For those looking to explore the series further on original hardware, you can find physical copies of the PlayStation 2 version on sites like eBay or Amazon, which offers a gameplay style similar to what a PSP port might have looked like.
You can find the Sonic Unleashed Java Port on community platforms like Game Jolt . 2. Emulation and Mods (PPSSPP) Sonic Unleashed Psp Rom
The PS3 version has been available on Sony's streaming service in the past, allowing for play on modern consoles. For those looking to explore the series further