There’s a pretty vibrant open source diabetes community in Germany. Some tools such as AndroidAPS and xDrip have been existing for a long time and work together with many pump and CGM models available through the health insurance. GPL-3.0 licensed.
At least these were very beneficial for me, A1c went down from 7.5 to 5.5% without many hypos. You have to compile AndroidAPS by yourself due to distributing binaries would not be legal. It requires some knowledge, but for my partner not needing to call an ambulance ever again when I have a nightly hypo, that is a big win.
No nightly hypos for the past five years I’ve been using these tools…