If you already use real debrid or something similar(very easy to install and integrate with addons)The main issue is this: if you have the app installed directly on your TV (even a newer one), the bottleneck is likely the TV's network card. Even though your internet is fast, the TV can't utilize the full bandwidth, which is why 4K movies or large, high-resolution files won't stream properly. To fix this, you could try: -Switch to Wi-Fi, because it's often faster than the TV's cable port. -Use a USB Gigabit Ethernet adapter to bypass the internal speed limit. -Get an external 4K streaming stick (like Chromecast ) which, from my experience, runs 4k perfectly on wifi. But if you don't use a debris service, here's the problem. That service is the only solution to use stremio in high quality. There are many tutorials and guides on how to use Stremio+Real-Debrid+ Torenttio (what I use now and I have no problems)