It seems LiveCharts development stopped several years ago and it does not support .NET Core. To use a .NET library in QM3, it must support .NET Core 3 or .NET Standard 2. Only look for libraries that are in active development. Maybe https://github.com/swharden/ScottPlot
QM3 currently does not support NuGet, which is an easy way to install and update .NET libraries and their dependencies. To test a .NET library, it's better to install the NuGet package in Visual Studio and test. Then, if want to use it in QM3, copy the dll (and dlls it uses) to the QM3 folder or the Libraries subfolder and add reference(s) in Properties dialog. You can download NuGet packages directly from the NuGet website, unzip (they are zip files) and take the newest dlls.
QM3 currently does not support NuGet, which is an easy way to install and update .NET libraries and their dependencies. To test a .NET library, it's better to install the NuGet package in Visual Studio and test. Then, if want to use it in QM3, copy the dll (and dlls it uses) to the QM3 folder or the Libraries subfolder and add reference(s) in Properties dialog. You can download NuGet packages directly from the NuGet website, unzip (they are zip files) and take the newest dlls.