I know you said no smartphone, but locus map on Android does everything, with voice navigation, rerouting, offline mode, gpx import export, tracking, route building, Bluetooth connection to speed and cadence sensor, etc. And on my tiny phone, the battery can last more than 10 hours with it running with automatic screen on/off which switches on each voice announcement at the time interval that you can set. There are so many options that it takes hours to learn every single one of them, but it's not difficult to just get started with simple navigation. I put the phone in a waterproof klickfix bag on quick release handlebar mount. The bag has space for a power bank in the back.