is there a way to upload folders to iCloud WITHOUT them taking up space on my machine?

No. Anything in iCloud is synced to your Mac. Yyou can Elect to optimize storage which May offload larger files provided space is needed on your Mac; it is not a user controllable process.

yes. you'll need to find some service that offers offline storage only.

I should add that this is not critical data I am uploading and I can just delete it from cloud anytime as I have a copy on a removable drive…….on a (spit) windows machine

Yes you can. But it is not ideal. I have 400gb in the cloud but my Mac has only 256.

Here is how I have done it. First load some data and sync to cloud. Then remove the downloads. The data remains in the cloud and you can force a download when needed.

The problem is if you reorganise your cloud data it tries to sync everything and you have to go through the remove download process again. I am going through this now and it may be more trouble than it is worth.

I suspect that updating macOS may also trigger a full download. I know that I should have bought more storage in the first place but I would rather pay Apple than another cloud supplier.

This is not a problem for me but it is fun finding out what I can do.