Catalyst Center (DNA, controls ios-xe) needs a lot of resources. Like x40 cpus 150G
They've released an OVA for DNA center but very weighty (x200 micro services / containers )
So don't use the OVA file. Take the installer that Cisco gives you to reinstall their physical appliances, which is just an ISO. Mount a VM with the requirements that I just stated. See this External Link
Now switches that are manageable by SD access or by DNA center to use as SD access nodes. 9000V. So if you have a distributed fabric, you're going to need, you know, four of these Catalyst 9000 virtual switches, which each take 32 gigs of RAM.