Hopefully that makes sense, I'm new to all of this.
Bluetooth is an absolute nightmare if you don't understand the majority of what's going on (which in and of itself takes... a lot of time). There's a bunch of logic going on and most of it is handled in callbacks that you will never see, except the dreaded timeout/failure to handle print at the end of the main loop. Zephyr will ease a lot of those painpoints, with the understanding that you're ignoring a lot of the machinery humming under your feet.
Things that stood out to me:
0. If this is your first embedded project / you're actually new to all of this, get ready to take a beating. "Abandon all hope, ble who enter here."
1. Do yourself a huge favor and get two* dev kits. Nordic provides walkthroughs on getting setup with two flavors of code (zephyr, or low-level drivers). Each has a tutorial for uart forwarding/handling. Expanding on that tutorial will take a lot of futzing around, or actually learning what the machinery is doing under the hood. Learning the stack did not come naturally / I found it very difficult. Why two? Two lets the bluetooth abstraction handle itself / you don't have to deal with it right away when you're getting started.
https://www.nordicsemi.com/Products/Development-hardware/nRF...
2. If / when you want to attach your bluetooth device to something more useful (e.g. a computer or mobile device), do yourself a second huge favor and develop using linux + a laptop. I tried to do development on windows + WSL and there were many, many hangups with the hardware handoffs from PyBlues to the local bluetooth drivers. Maybe it's gotten better, but I doubt it. My other alternatives were driving direct from Windows bluetooth libraries (behemoths that would take time to setup / understand), or develop for mobile (which also will take time to setup / understand). Neither was an enjoyable experience.
so in summary:
Is Zephyr overkill? - Absolutely. But the path is well trodden.
Regardless, Zephyr is an RTOS which provides OS functionality like scheduling, interrupt handling, semaphores, etc.
It is most likely overkill for what you are attempting to do. You should instead look at the vendor provided SDK for the nrf52 chip and program it bare metal. The SDK is most likely just libraries/drivers and does not come with an RTOS.
Would something like circuitpython not be easier to work with?