The on-by-default telemetry and license restrictions come to mind
https://github.com/VSCodium/vscodium
It is a repository of scripts to automatically build Microsoft's 'vscode' repository into freely-licensed binaries with a community-driven default configuration.
I didn’t know this until recently when someone pointed it out.
https://github.com/dotnet/core/issues/505
Thought it was relevant since OP is talking about a Linux IDE for C#
The on-by-default telemetry and license restrictions come to mind