This is helpful, thank you.

We have 121s and retrospectives in place, so I'll focus on helping people to feel safe enough to give honest feedback/suggestions in those sessions.

I like the idea of framing the question differently, rather than asking "what can I do better", people may feel more comfortable answering "what areas can be improved upon" (we already use that question as a starting point for process changes in retrospectives, but asking it to ICs in 121s is something I can start doing).