Ask HN: Leetcode for Back End and Server Development

I am compiling resources for a platforms similar to Leetcode (kata kind challenges) focused on backend development. I am aware of few of the resources which i've listed down below, will appreciate if you guys can share bit more.

- https://hackattic.com/ : Interesting programming Problems.

- https://sadservers.com/ : Learn Linux by solving problems.

- https://fly.io/dist-sys/ : Distributed Systems Problems.

- https://github.com/pingcap/talent-plan/ : System Programming / Distributed System Challenge.

- https://protohackers.com/ : Server Programming Challenges.

- https://codecrafters.io/ : Implement server tech / softwares from scratch.

- https://hyperskill.org/ : Lots of projects based tutorials.