Might not the thing you are looking for, but I tried to find a replacement for Keep a year ago and somehow stuck with a todo.txt (http://todotxt.org/) file. It can be edited in a normal text editor but I use Markor and todo.txt on Android and Sleek on desktop. Sync is fine via your preferred sync tool.
Thanks! The systemd option doesn’t sound to bad. I managed to avoid it till now, but I guess it is time update my ~10-year old linux knowledge at some point, haha.