You bought what you bought, it has the features it has, and the manufacturer doesn’t hide those features. The 1824c has 8 analog output channels. We can spend all day questioning why it only has 8, but the reality is it has 8 because that’s the way it was designed. Not everything has everything everyone needs. Essentially it looks like the design lends itself to having two stereo feeds, like a control room output and a studio output, with dedicated level controls and mute functionality, which is pretty cool, and then there are 4 additional analog outputs for whatever you want to do with them. It’s a nice design compared to some other boxes that fall short of those control room features. Additionally it’s flexible enough you can use all 8 of the outputs as discrete outputs and feed those however you want using your ITB routing. So that’s what you have. You say you do not need 10 channels, you only need 8, but then in the next sentence you ask how you can have 8 discrete feeds plus a separate stereo mix output. Well, then you need 10 channels, not 8. And the 1824c is not the right box for you if you need 10 D/A output channels. And there’s no mystery it only has 8 analog outputs. You’re discovering what you need. And nobody else can read your mind or the future as to what you need now or will need. I have a Digimax FS and I love it. It’s older, but it’s been a great piece of kit for me from Presonus, so I might have recommended the 1824c as well based on my experience with a legacy product. I probably would have also asked you how many input and output channels you need. At the time you bought it you might not have known the answers to those questions and so it might not have been helpful to ask. But nobody else is responsible to know what you need now or in the future, and your understanding of your needs is changing and that happens. If you have other boxes that can meet your present needs can you just use one of them instead of the 1824c?
