jEdit is becoming really rather a good text editor. It’s a while since I’ve looked at it, but it now has a lot of nice features, and a large number of plugins with which you can extend it. Being Java-based, you can use it on a wide variety of platforms.
It takes some time to get into, customize, etc but I can see it might be worth persevering. Nothing worthwhile, as they say, was ever achieved without hard work. (Who said that, besides my mother? Albert Schweitzer? It’s his sort of thing, but it probably predates him)