Supporting SQLite as an option for people with modest needs is not a bad idea. As long as you keep your SQL simple and avoid vendor-specific extensions, adding support for it at any point shouldn't be difficult.

Providing a Docker config is fine, but I would never lean on it as a substitute for conservative dependency choices and good build scripts. Many people don't use it and never will. If you instead design your software to be easily built/installed/packaged natively for any distro, then it will reach more users, and as a side effect, will also be easy to package for just about any container system (Docker, Kubernetes, LXC, etc.)