If I could find something that offers a “run this cli command on file saving”, that’s really about the biggest requirement I hope to have in place.

You can do that via CLI, too, by the way. You can watch your source code directory for file changes with entr: https://manpages.org/entr
Make sure to see the examples at the end of the man page, since usage isn't entirely obvious...

And if you want KDevelop without being so focused on KDE development, then that's basically Kate: https://kate-editor.org/
If you install the LSP servers for your toolchain (and check that Kate auto-starts them), then it can assist pretty well for different programming languages (i.e. virtually indistinguishable from VSCode, as far as I'm aware).