Looking for a future-proofed Android box around $50

So I already have an Android box running LE but it already has a couple of years under its belt and I wanted to update my hardware, especially since I also recently bought an OLED TV. Thus, I'm trying to find the best option but as always, it's really easy to get lost in all the CPU architectures, RAM options etc. - and so, as with my previous hardware questions, I come to you!

Is there anything you would now recommend for around $50 that would be suitable for mostly 1080p but also occasional 4k content off a USB flash drive with an option to possibly install LibreELEC in the future? I don't know if I'd do it right from the get go but just wanted something future proof. Movies off a USB stick will basically be the only thing I'd need from the device - to offer playback without hiccups and with no subtitle problems. The budget is a bit fluid, if something is worth it and costs even less, that's even better What would you choose?

Thanks a lot in advance!

Thank you. However, an RPi is way less plug and play than an Android box, and like I said I may not install LE right away but would want the device to be operational from the get go anyway