The device has extremely slow flash chip. It takes close to 20 minutes to flash, you have to flash combination of oem bootloader block +openwrt concatenation , then only sysupgrades. my V4 is a bit faster still 6-7min for sysupgrades.
Serial header is right next to live mains prongs to make recovery more memorable.
Use smaller older image (prepared with oem boot block) without luci to not lose patience during first install. Then sysupgrade to 23.05.2 until situation is clarified.