FYI there are different DIY bitcoin hardware wallets displayed in this Telegram chat: t.me/DIYbitcoin

I'm most partial to the Specter DIY, then Krux. I like how Krux has several options for devices. If you want something simple, just buy the Maix Amigo then flash it, but if you really want to DIY you can build the Maix Dock (soldering involved). Just need to print a case for it now! https://t.me/DIYbitcoin/4839