I'm using an ESP-01S with a USB programmer based on the CH340C chip, connected to a Linux machine. After some poking around, I was able to upload a sketch using esptool.py using a baud rate of 74880, but that's not an option in the IDE, and editing my boards.txt didn't change anything. Normal serial communication works fine in the IDE. Attempting to upload at other rates via the IDE results in this:
esptool.py v3.0
Serial port /dev/ttyUSB0
Connecting........_____....._____....._____....._____....._____....._____....._____
A fatal esptool.py error occurred: Failed to connect to ESP8266: Timed out waiting for packet header
I don't see a way to force a custom baud rate anywhere, nor have I been able to find a way to change the rate on the ESP01/CH340 side, but I could be missing something. Any suggestions would be appreicated.