Finally, I can confirm that it's possible to use the FireWire interface from the Catalina, and further from a 2019 Mac Pro (aka 7,1). I'm using the Apple TB3->Tb and TB->FW800 adaptors. Even without the kext installed, you should be able to check "About This Mac" and see the card connected when you check FireWire. But it won't show up in Audio MIDI Setup or your favorite DAW without the kext.
Don't use the driver installer, or at least avoid it. If you don't have a copy of the drive itself (IFFWDMmkII.kext), you could install it and then retrieve it, probably the easiest way to get it out of the installer, but might need to do some work to back it out and put it in correctly.
The bottom line is that if the Mac hasn't popped up a dialog telling you that if would really want to install it, you'll need to do it in Security & Privacy panel, then it hasn't been installed right.
You could copy and transfer IFFWDMmkII.kext from /Library/Extensions in your old computer. Don't install it yourself, though. If the command shell makes you nervous, there is a tool for Hackintosh use, Hackintool, that will do these same steps for you plus a few more just in case.
You need to disable Gate Keeper and mount the System Partition as read/write; in Terminal:
sudo spctl --master-disable
sudo mount -uw
sudo killall Finder
Then copy the kext. you can type "sudo cp -R " and fill in the path to the kext by dragging it into the Terminal window, then finish typing the rest of the copy command (/Library/Extensions); here I've assumed you put it in your user Downloads folder:
sudo cp -R ~/Downloads/IFFWDMmkII.kext /Library/Extensions
Here are some safety things, the most useful being to make sure the user:group is root:wheel (this will hit all extensions), and ensure the permissions are right too:
sudo chmod -v -R 755 /Library/Extensions
sudo chown -v -R root:wheel /Library/Extensions
sudo touch /Library/Extensions
Then, you need to rebuild the kext cache:
sudo kextcache -I /
Finally, restart your Mac.
If anything goes bad, or you tried to installed in a way that didn't work before, you'll get errors until you back it out. Removing the kext from /Library/Extensions is not sufficient, you'll need to remove it and run the kextcache command. Extensions are staged in /Library/StagedExtension/Library/Extensions, which looks like a copy of the /L/E directory, except that you can't remove the files directly. So, if it gets built with the wrong status, all attempts at installing the kext will fail. I initially got most of this info from https://www.tonymacx86.com/threads/...an-sierra-high-sierra-mojave-catalina.268964/ but was stuck at that point with it failing till I figured the rest out. Note that link is largely Hackintosh oriented, so it might be confusing.
Don't use the driver installer, or at least avoid it. If you don't have a copy of the drive itself (IFFWDMmkII.kext), you could install it and then retrieve it, probably the easiest way to get it out of the installer, but might need to do some work to back it out and put it in correctly.
The bottom line is that if the Mac hasn't popped up a dialog telling you that if would really want to install it, you'll need to do it in Security & Privacy panel, then it hasn't been installed right.
You could copy and transfer IFFWDMmkII.kext from /Library/Extensions in your old computer. Don't install it yourself, though. If the command shell makes you nervous, there is a tool for Hackintosh use, Hackintool, that will do these same steps for you plus a few more just in case.
You need to disable Gate Keeper and mount the System Partition as read/write; in Terminal:
sudo spctl --master-disable
sudo mount -uw
sudo killall Finder
Then copy the kext. you can type "sudo cp -R " and fill in the path to the kext by dragging it into the Terminal window, then finish typing the rest of the copy command (/Library/Extensions); here I've assumed you put it in your user Downloads folder:
sudo cp -R ~/Downloads/IFFWDMmkII.kext /Library/Extensions
Here are some safety things, the most useful being to make sure the user:group is root:wheel (this will hit all extensions), and ensure the permissions are right too:
sudo chmod -v -R 755 /Library/Extensions
sudo chown -v -R root:wheel /Library/Extensions
sudo touch /Library/Extensions
Then, you need to rebuild the kext cache:
sudo kextcache -I /
Finally, restart your Mac.
If anything goes bad, or you tried to installed in a way that didn't work before, you'll get errors until you back it out. Removing the kext from /Library/Extensions is not sufficient, you'll need to remove it and run the kextcache command. Extensions are staged in /Library/StagedExtension/Library/Extensions, which looks like a copy of the /L/E directory, except that you can't remove the files directly. So, if it gets built with the wrong status, all attempts at installing the kext will fail. I initially got most of this info from https://www.tonymacx86.com/threads/...an-sierra-high-sierra-mojave-catalina.268964/ but was stuck at that point with it failing till I figured the rest out. Note that link is largely Hackintosh oriented, so it might be confusing.