In short, there are many options, both in theory, and in practice for the REPL without IDEs like Juno or VSCode or with them (also supporting the other less used IDEs?).
Those are the most used, while be aware about GitHub - JunoLab/Juno.jl
Attention : We have decided to join forces with the Julia extension for VSCode. As such, this Atom-based plugin is effectively in “maintenance-only mode” and we expect to only work on bug fixes in the future.
FYI: old blog post: A Julia interpreter and debugger
There are many threads on debugging, most likely outdated, I’m just not sure as I do not use the debuggers:
The Rebugger (not a typo) sound cool though. There is support in Julia 1.5 for time-traveling bug reports, so I foresee a future where the debugged can go back in time, not just step forward, if not done already. Then in VSCode.