Do I need a subscription to use an indoor cycling bike?

No. Budget and mid-range bikes from YOSUDA, Merach, JOROTO, Schwinn and CHAOKE all function fully with just their onboard console and manual resistance, and most are Bluetooth-friendly with third-party apps like Peloton, Zwift or Apple Fitness+. Only Peloton's own ecosystem effectively requires an ongoing membership to unlock its core class library, a point repeatedly raised in r/homegym and r/cycling threads.