This has been my experience as well (as a dev). Curious if there's others in the same sort of situation, and I'd love to hear more thoughts. My general tips are:

- Use as much as you can of what they already have.

- Talk to them, but don't waste their time.

- Follow their patterns.

- Understand at the end of the day its their domain.

- Choose your advice carefully.

- Try to throw a little extra gratitude their way. Organizational visibility, code reviews, documentation, mentorship, whatever feels appropriate and not over-stepping.

- Put extra effort into handoff documentation.