The Vodafone Smart Tab 3G’s stock firmware is available online. /e/ os might be able to blow new life into this old device.
You certainly have no idea how much work it takes to build a new custom ROM. The Vodafone Smart Tab 3 10" from 2012/2013 with 1.280 x 800 px display, 1 GB RAM, 16 GB internal memory and Stock Android 4.2.2 (Jelly Bean) has in my estimation no chance of a custom ROM, neither /e/ OS nor LineageOS.
You can have a /e/ OS experience with the comparable Tablet Samsung Galaxy Tab 2 10.1 (P5100) (espresso3g). In June 2020 it was updated by @Android-Andi - probably the last time.