I have also found #TaskChampion! https://taskchampion.github.io/taskchampion/ But for now, I am settled with #TaskWarrior. I have also scripted a small Bash-integration, so that my Ad-hoc NextCloud Notes taken on my Android Phone (starting with Task or Log) are automatically added to my TaskWarrior DB whenever I use my Laptop! Auto backup of my DB is done via NextCloud Sync Client (no need to operate Task Sync Server atm).