Integration using the 'generic' option is not as simple as selecting 'generic' and things will work. The 3rd Party IPAM needs to meet certain API requirements and I am not sure that Solarwinds IPAM meets these with their off the shelf versions (maybe in the latest versions). There probably would need to be some customization on Solarwinds side.
Here are some links that may help...
"Two third party integration modules are included in Cisco DNA Center, as shipped, one for IPAM Provider Infoblox and one for Bluecat . Other IPAM Providers may be configured for use with Cisco DNA Center by providing an IPAM Provider REST API service that meets the Cisco DNA Center IPAM Provider specification."
IPAM Provider Integration Requirements
Any new updates on Solarwinds support? I can't find any resources online and our Cisco account manager seems to be struggling to find info too. I must say I am disappointed in DNA, what the marketing documentation says and what is truly possible out of the box without external components are two different stories. For the price of the DNAC I would have expected more.