I recently upgraded my ancient Lenovo P2, which is still a very good phone, from stock 7.0 to Lineage 18-20. Each one worked fine... except... the battery life went from 2 days to about 18 hours. I never found a solution for it, unfortunately so "upgraded" to 8.1 and I've getting amazing battery life now, even better than before. Luckily I barely install anything except Youtube, Newpipe, Maps and Signal. If anyone knows a solution to battery drain issues in Lineage, I'm all ears! Thanks.