CGMs (of any brand) are not, and have never been, reliable in the way that this story implies that people want them to be reliable. The physical biology of CGMs makes that sort of reliability infeasible. Where T1s are concerned, patient education has always included the need to check with fingerstick readings sometimes, and to be aware of mismatches between sensor readings and how you're feeling. If a brand of CGMs have an issue that sometimes causes false low readings, then fixing it if it's fixable is great, but that sort of thing was very much expected, and it doesn't seem reasonable to blame it for deaths. Moreover, there are two directions in which readings can be inaccurate (false low, false high) with very asymmetric risk profiles, and the report says that the errors were in the less-dangerous direction.
The FDA announcement doesn't say much about what the actual issue was, but given that it was linked to particular production batches, my bet is that it was a chemistry QC fail in one of the reagents used in the sensor wire. That's not something FOSS would be able to solve because it's not a software thing at all.