@TrueFalse, QEMU, via this OSX-KVM project.
I had to check out an older version, because their master no longer works for Catalina. And tweak the network args to QEMU, as the defaults were wrong on my host system, and you need networking to install. 
I believe this is the same issue I am having which I am in truth feeling very nervous about. I have Catalina and I can’t open Daedalus. I am updating to Sequoia now. If it doesn’t work I’m not sure what I will do as I’ve used this wallet for a long time and don’t know how to access it other wise. The 12 key phrase I’m sure is long gone 
You should never – on any chain – continue using a wallet without knowing the seed phrase for longer. It can always happen that a wallet app goes out of business, your computer crashes, whatever else. Only with the seed phrase (and/or maybe a hardware wallet) you have the flexibility to use another compatible wallet app.
Moreover, if it really is a 12 word seed phrase for Daedalus, then it is still a Byron wallet (Ddz… addresses). Support for those is pretty limited by now. Apart from Daedalus, only adalite.io and adawallet.io still have them. The switch to Shelley wallets was four years ago and all other wallet apps support only them.
Wish you luck that you get Daedalus running and would strongly suggest to create a new wallet with any wallet app you like – https://cardano.org/what-is-ada/#wallets – and send everything over.
I’m downloading the most recent Mac OS so I hope it works, I thought Daedalus was the most solid Cardano wallet so I was orienting around it being solid for some time. Is this not the case?
Just so I’m clear, is there any reason that Daedalus shouldn’t work at this point with an updated OS?
No, should work.
It is solid up to now – if it still is the most solid Cardano wallet app now, don’t know, but there is no immediate reason for concern that they will just vanish completely.
But it does eat up more and more resources. We already had a lot of users whose computers couldn’t keep up anymore and who are much better served by one of the many good light wallet apps.
And even when continuing to use Daedalus, moving to a new, more powerful computer is very complicated without the seed phrase. Operating a wallet without knowing exactly where the seed phrase is just a very bad idea (and I believe every wallet app including Daedalus says so during setup).
They never made it necessary to migrate from Byron to Shelley, but it would have nevertheless been and still is a good idea to do so to be able to use alternative wallet apps whenever necessary, to be able to stake and participate in governance etc. pp.
Hi all, Daedalus 7.1.0 has just been released, and it contains the fix for this issue.