I'm happy to take bug reports and pull requests if you want to help improve Time Cop, but I fundamentally want to keep this app relatively small and simple. If that's not for you, there's plenty of other options out there.
The app is created pretty much entirely in Dart using Flutter, and I tried to make heavy use of the Bloc pattern.
Here are a few resources to get you started if this is your first Flutter project:
For help getting started with Flutter, view its online documentation, which offers tutorials, samples, guidance on mobile development, and a full API reference.
After installing and setting up Flutter (ideally its latest version) and downloading the Time Cop code, you can simply build and run this Flutter project.
When building for Linux, you will need to install libsqlite3 development packages first. On Debian-based distros, you can do so with this command:
sudo apt-get -y install libsqlite3-0 libsqlite3-dev