You can run Armbian and DietPI (both Debian derivatives) on most small boards; some like the NanoPI NEO are in the same price ballpark as the Pi Zero, but are in stock.
This new breed of similarly price low cost SoC is an awesome alternative to ESP-32. It has MMU for full Linux installation, NPU for AI processing and network peripherals for IoT [1],[2]:
I have a BBB in a drawer somewhere. It's a very nice platform, but I quickly realized that for the $50, I could use a $30 RasPi B+ (back when you could get them) talking to a $2 arduino clone and accomplish the same thing far more easily.
https://www.friendlyelec.com/index.php?route=product/product...
https://www.armbian.com/download/?device_support=Supported
https://dietpi.com/#download