Hi Frederick,
An alternative is not to use the Silab drivers.
With the changes Apple made to MacOS extensions with Catalina (or was it Mojave?), I de-installed the Silab drivers and now let MacOS use it's inbuilt drivers. I've not had a problem and can connect seamlessly to any of my Icoms ('7610, '9700 and 'R8600). I have a 2017 tbMBP with Big Sur.
73, David VK3DRH