My first comment would be that free software made by a corporation is still free software. Like Eclipse, which was originally made by IBM and is a huge ecosystem, especially for "java and friends." So, there is nothing wrong with VS Code(ium). It is a "proper" open source editor and a very good one (I don't use it though - I prefer EMACS).

As for community-base alternatives (which is probably what you mean), you could consider kdevelop or pulsar. There are other alternatives which are equally good and surely one of them will fit your purpose. You mentioned Kate and I can't find anything wrong with it, especially once you start installing the plugins that are relevant to what you do. Same with Gedit.