How often do you need to regenerate your seed? That hour is more than short enough for me.

For me, it compares disfavorably to just having an ESP8266 generate the seed for me.

use the offline tool. will take you 30 seconds.

https://www.ledgerwallet.com/support/bip39-standalone.html or https://github.com/iancoleman/bip39

PS: even a 24 word checksum takes just a couple minutes

It'll take me 30 seconds to use, but setting up the Raspberry Pi and formatting the SD card afterwards is a hassle. You can't beat the ESP8266 method, since you can just look at the code and be sure what it's running.

I'm not sure the ESP8266 is a great way of accomplishing the goal of being able to know what's running by just looking at the code, unless the Espressif has suddenly opened their firmwares and toolchains. An AVR (like an arduino) would probably be better suited for the task, as the open toolchains are mature.

What would Espressif be able to do? Somehow retain the entropy it gave to the code that you used to generate the key and then send it to their servers when you reflashed with an unrelated program and connected to WiFi? That seems a bit far-fetched.

Regardless, sure, the Arduino is also a good platform to do this on. It doesn't run MicroPython, though, so I implemented my particular program on the ESP for speed/ease of development.

Don't forget the Debian bug that created weak keys from 2006 to 2008. These sorts of things happen. It's best not to attempt to disparage the possibility.