In AppData\LocalLow\Three Eyes Software\Silverpine\ModelDefinitions\Gemma-2-Large.json replace
"skipSealCheck": false,
with
"skipSealCheck": true,
Then manually download the model here, rename it to "Gemma-2-Large.gguf", and put it into the KoboldCPP folder as normal.
If you have a very slow connection there is probably a chance of the download randomly failing at some point.
mono-io-layer-error might also be a Unity bug.