Graphic card - upgrade need ?

Neither computer has enough RAM installed, at least 16GB is still ok for most use but getting iffy for larger images. Go with 24 or 32GB if possible.

A new video card for the desktop will be a huge help, as Ged noted. And an SSD will make a big difference.

Having said that, neither of your computers will be supported by Windows 11. Instead of sinking money into old hardware, you are likely better off buying new kit with a proper video card, more RAM expansion, SSD storage, USB-C/Thunderbolt, faster networking, a warranty, and Windows 11 bundled. Sell the old desktop, add RAM to the laptop and keep it as a backup.

The system says it's a DirectX 11.0 problem even though I have the latest drivers installed and DirectX 12.0 on Win10.

By @petrb43367114

Just to clear that up: Photoshop requires a GPU with DirectX Feature Level 12.0. That's actually not the same thing as DirectX 12 support. Yeah, it can be confusing. But feature level is what the card can do, its hardware performance level.

DirectX 12 is a set of APIs (application programming interfaces). So the card can understand the calls and commands, and "speak the language" - but not actually be able to execute it if it doesn't have the necessary feature level..

@petrb43367114 for the PC, I would go with an RTX 3050 or similar, providing the power supply you have can take it.

RAM I would increase to 32GB, you haven't mentioned what storage you have, but if it's an HDD drive replace it with an SSD of about 500GB or more.