Can you elaborate more on how you use it or do you recommend any codebase to learn more?
I remember evaluating Kermit and ymodem for my embedded work too, but didn't end up using them. Maybe I didn't understand Kermit fully. I wanted something to connect over serial (usb cdc and ble) via the browser and manage files and the state of the device.
I always end up writing something worse and half-baked in the end..