I think the Bowser wallet is a neat project, but should only store small amounts of bitcoin, if any. Have you tried flashing the AWS one? I don't think it works
No I didn't and I don't have AWS M5Stack device to try it.
Bowser is just a fun little project and there are much better DIY devices that exist today, like SeedSigner, Krux and other stuff made with RapsberryPi Zero devices and Trezor code.
I am following all open source hardware wallets and signing devices in one of my topic, so anything new and interesting that comes out will be posted there:
https://bitcointalk.org/index.php?topic=5288971.0