Upgrade 25.11 to 26.05: no extra screens with USB-C docking station

Hello; I use NixOS on a Thinkpad with a USB-C docking station and two external screens. This works fine with 25.11 but going to 26.05, the screens are not detected and don’t work. Any ideas why? Here is my configuration.nix. Where should I start looking? I don’t know what extra information to give here as I’ve found that saying too much in the OP means that people don’t read it.