I am also using open webui. Most LLMs are too verbose for me, so I created a model in open-webui with system prompt “Do not repeat the questions. Avoid giving lists as answers. Do not summarize the answer at the end. If asked a follow-up question, respond with only new information, do not repeat previously stated information.” and named it No Nonsense.
Are you using a custom rom? I don’t have this option on my oneplus 9 pro. but I have something else.