I've always associated Amigas with AmigaOS, and this is the first I heard about Unix. Why would you replace AmigaOS with Unix? Is it because it would be substantially cheaper than other 68030 Unix workstations?
In addition to Commodore there were Apple, Acorn, and Atari also making these upscale plays with Unix. Sun and NeXT were native to this market. And non-Unix workstation vendors like Apollo were adding compatibility.
It was a crowded market and Commodore didn't bring anything unique to it. The Amiga's multimedia strengths were practically wasted running X Windows.
AMIX was actually one of the first gcc targets, as mentioned here: https://www.reddit.com/r/amiga/comments/1ikyw0s/the_fsf_free...
It seems it may have had a pivotal role in the history of the FSF. So, clearly, someone found value in it!
Only then folks started reaching out to GNU, as means to avoid paying for UNIX developer licenses from their respective vendors.
Sun even had multiple levels, one of the reasons Ada didn't took off, was that UNIX vendors like Sun had it as an additional SKU, the developer license would only get the classical UNIX stuff, alongside C and C++ compilers.
I was really happy they went and did their own thing, classical UNIX was never great at multimedia.