Interesting that the ECS you linked beats out Flecs .net bindings. I wonder if it is because of copying to/from the dotnet heap.
Looking over the readme.md I find it interesting they don't list dotnet 9 support but they do list 7 so they do seem to support non-LTS versions but skipped 9 (mind you maybe they just didn't update the readme?)
Up until midway through Hades 1 development Supergiant was a c# shop with their own engine on top of libraries (the fact they rewrote their core tech in the middle of a game project that was already available to the public remains insane to me).
C# is a super underrated language and Monogame has just enough batteries to get going without being in your way too much.
For ECS, I've been using Friflo ECS and haven't had issues so far: https://github.com/friflo/Friflo.Engine.ECS