I have 2 mods that does not enter DFU@USB with BOOT0 pull-up: Hotcig RSQ and Vandy Vape Pulse 80W. I suspect some activity on other peripherals (USART/I2C) that override DFU over USB. I don't remember if there is SWD pads somewhere under display, if so, you can try to connect ST-Link and flash bootloader with it (pin 34 is SWDIO & pin 37 is SWCLK). But I'm still suspect USB hardware issue I haven't bought it yet. Probably, it will Yep, it is unofficial, just for fun. https://nfeteam.org/forum/threads/vaporesso-swag-armour-pro-hotcig-rsq-vandy-vape-pulse-80w.2289/ No way.