What DIY hardware wallet options are there? I found the following:
Prices are rough estimates, I even assumed 1 EUR = 1 USD for simplicity, some hardware listed here is actually difficult to find like Maix Amigo which might be available in one place for just $50 in the other place to be as expensive as $90, Raspberry Pis are even more difficult to put one specific price on assuming they are even available.
1. SeedSigner
Raspberry Pi Zero based but works with any version of Raspberry Pi + camera + display with buttons.
Cost: parts > 55 EUR/USD, kits that include 3D printed case > 65 EUR/USD. Good option for those who already have a Raspberry Pi lying around. Contrary to DIY Jade and Krux (I don't know about Specter or PiTrezor) allows importing multiple wallets in the same session, so you can freely switch between wallets what makes working with multisig wallets very convenient. Assuming we use Raspberry Pi without WiFi/BT module our HWW will be fully airgapped (PSBTs via QR codes).
Project website
GitHub
Crypto Guide video
BTC Sessions video 1
BTC Sessions video 2
2. DIY Jade
Works with multiple ESP32 hardware options. Very budget friendly (as cheap as just around 10 EUR/USD for the most crude TTGO variant) if you are happy with using it connected via USB. Air gapped option require adding camera (no guide on that available yet).
GitHub
Crypto Guide video
4. Krux
Works on some devices equipped with RISC-V Kendryte K210 CPU such as M5StickV and Maix Amigo.
Cost: M5StickV similar to SeedSigner (so around 55-60 EUR/USD), Maix Amigo more (80 EUR/USD, hard to find actually) but worth noting that both M5StickV and Maix Amigo are already assembled with display, camera, and battery, no need to source parts separately and chassis is nice and compact.
GitHub
Crypto Guide video on M5StickV
Crypto Guide video on Maix Amigo
5. Specter
Uses STM32F469I-Discovery board, niche and expensive but feature-rich hardware with big screen.
Cost: around 75 EUR/USD + optional camera (for reading QR codes in air gapped ops) for around 40 EUR/USD, 3d printed case also around 40 EUR/USD, so rather expensive and physically the biggest of all listed here but probably the best option for those with big fingers and/or bad vision (comparable only to Maix Amigo from this list).
Project website
GitHub
Specter YT Channel
6. PiTrezor
In the cheapest variant requires only a Raspberry Pi Zero or RPi 4, can use the same hardware as SeedSigner with an option to use a display of lower resolution than SeedSigner (the latter needs a specific model with 240x240 px, PiTrezor requires only 128x64) or even can simply use Pi's HDMI output. No need for camera as it is a Trezor clone.
Project website
GitHub
Crypto Guide video