This is a self-hosted port of a fairly old prototype I made in May 2023 (pre GPTs era): https://github.com/dubesor/gptchars.
Currently I implemented a mix of 3.5 Sonnet, Llama-3.1-70B (+Nemotron) & 405B, Deepseek V2.5, 4o-mini, Command R and 3.5-Turbo.