I have a partial fix for the Silhouette cutter, but it works. Absolutely not happy about how I had to attack this one, but even if I bought a Cameo 4 Plus to match my 15" Cameo 3 the software would still be broken. Gah...
Anyway, the solution for these newer Macs is to purchase SCAL, either base 6 or 6 Pro; I went with 6: [https://surecutsalot.com/software/software.php|SCAL purchase page|new_window=true]
They need to update this 1st party software, but at least if you're going to throw $2k+ on a new Mac $60 is a nuisance.