A teammate of mine has sometimes delayed tasks and informed about them at the last minute leading to us missing the delivery deadlines. As the tech lead, I've shared this feedback along with explaining the impact and suggestions to tackle the issue. I've encountered this situation a few times even after sharing this feedback.
What other steps can I take to help the teammate and minimise the overall impact on our delivery?
How do they inform you at the last minute? Is it a private message to you, and you have to explain the delay to others and effectively handle the mess? If so, I'd encourage you to create a process where there is more accountability.
The point is not to shame them, but to bring more visibility to project deadlines and what has slipped for future planning. Some options of doing this:
You're also asking (smartly) about how to minimize the overall impact. The answer here is that you need to make a judgment as the TL around who you trust to get things done, and where you need more buffer or redundancy.
Trust is earned, and if you feel like this person is unreliable in delivering projects on time, you should either reduce their scope or have a "backup" engineer who can fill in as needed. This is something you should also discuss with your manager.