Petr Škuta The latest operating system macOS Catalina has been tested for quite some time. Even so, not all errors escaped. The latest one concerns problems with external graphics cards.
While the use of external graphics cards is not the concern of most users, there is a group that relies on them. We have bad news for you, as macOS 10.15 Catalina has v the current build has a problem with a number of them working.
Pro users are probably not too excited about macOS Catalina. Apple has removed support for 32-bit applications, replacing iTunes, which DJ software relied on, Adobe is once again having trouble optimizing Photoshop and Lightroom, and now there are problems with external graphics cards.
Users report that after upgrading from macOS Mojave some AMD external graphics cards stopped working on Catalina. Namely, it concerns the AMD Radeon 570 and 580 series, which are also the most affordable and therefore the most popular.
Mac mini owners report the most problems. The following are the owners of officially unsupported external boxes, but they have supported graphics cards in them, which worked with Mojave without problems.
Computer freezes, crashes and unexpected system restarts
However, the cause cannot be identified. For example, cards plugged into Apple-approved Sonnet boxes don't work either. On the other hand, most owners of the most expensive AMD Vega cards do not complain and their cards seem to work without problems.
The most common causes include complete freezing of the computer, frequent restarts and crashes of the entire system, or the computer does not start at all.
Gallery
It must be noted that we are really talking about supported AMD cards. So these are not cards made available manually by modifying the system libraries. Paradoxically, they can work.
Unfortunately, we also experienced similar problems in the editorial office. We combine MacBook Pro 13" with Touch Bar 2018 with eGPU Gigabyte box AMD Radeon R580. The system works until the computer goes to sleep and then does not wake up. In macOS Mojave, however, the computer with the same card woke up fine.
Unfortunately, the current beta version of macOS 10.15.1 does not bring a solution to the problem.
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Amaya Toman 
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Coincidentally, I have a borrowed Blackmagic Pro 580 EGP at home and I have no problem. I have a MacBook 15″ 2016. The problems are currently in Windows with this card, but that will be more the fault of Windows via BootCamp. Apple never officially supported this option, but it could be connected. So we'll see how it goes over time. Otherwise, I simply don't notice any errors. I don't use e-mails or any 32-bit applications, and even if I did, there was enough time to prepare for it.
Of course, it's a shame that even though the system has been tested in betas for so long, it ends up like this. However, the worse macOS is lately, the worse Windows is. Everything I have to deal with with clients on Windows at work is absolutely horrible. If I ever have to think about leaving Apple computers, I'll either replace them with a tablet or go back to Linux.