Does anyone know of a good Linux native mix reference tool, such as https://www.producerspot.com/magic-ab-2-utility-plugin-by-sample-magic ?
People pay for that? That’s just an A/B switch. You don’t need a plugin for that. That’s got to be the most basic thing to do with a DAW.
Use the PFL button.
Yes, yes I know it’s pretty basic, but these tools can be pretty handy actually. The ability to swiftly check against several reference tracks, match the loudness of the reference track to the loudness the mix, instant meter displays of reference tracks (e.g. peak and LUFS). It can all be done manually, I know, but the whole point of the tool is to simplify and consolidate the process into fewer steps. Anyway, I found the SampleMagic plugin to be pretty useful when I was still working in Windows.
All those meter types (and more) are built into Ardour. Set your reference mixes in tracks that aren’t feeding into the main out, and toggle any of their PFL/AFL buttons to do A/B comparison between your mix that reference track.