If you don't want to use Visual Studio Code here's alternatives IDE with open source.
Here's three open source alternatives:
Go to Brackets website
Eclipse Che IDE
It is a cloud-based IDE and runs on a SaaS model. However, this is a full-fledged open source project. If you have an instance of Kubernetes, you can completely transfer it to yourself.
Go to Che website
Atom is ideal if the extensions you need already exist or are ready to write them.
Go to Atom website