Just as a quick usability feedback: As long as Deepl translates asynchronously as I type, while Kagi requires a full form send & page refresh, I am not inclined to switch (translation quality is also already too good for my language pairs to consider switching for minor improvements, but the usability/ speed is the real feature here).

This is coming from a user with existing Kagi Ultimate subscription, so I'm generally very open to adopt another tool if it fits my needs).

Slightly offtopic, slight related: As already mentioned the last time Kagi hit the HN front page when I saw it: the best improvement I could envision for kagi is improved search performance (page speed). I still encounter multiple second page loads far too frequently that I didn't notice with other search engines.