Is it true that windows IoT remote client does not work with Raspberry Pi 3b+?
My Raspberry Pi is running on Windows 10 IoT core, and I tried to use remote client to control it, but the connection time out every time.
The connection time out every time...
This cannot possibly be evidence that the remote client will not work with a particular system -- it could only be evidence that it is flawed beyond reason and does not work with anything. Let's rule that out.
The reason this is the case, and why this is a duplicate, is explained in the answer to the duplicate.
Something which will not cause this is if the machine is reachable, but the [any server application of any kind] isn't running. That will generate an immediate response from the operating system on the machine reported as "connection refused"
Something which will not cause this is if the IP address or hostname is correct and the Pi is on the network but some piece of configuration is wrong.
There are only two possible explanations for "connection timed out".
The IP address does not belong to a reachable machine. E.g., if you disconnect your router from the internet and try and reach google.com, you will probably get "connection timed out". This does not mean google is broken or refusing your machine.
The IP address belongs to a machine which is intentionally configured to pretend it is not there. This could not happen by accident (except perhaps, an accident in configuring a firewall).
To summarize: "Connection timed out" cannot imply something doesn't work on the remote Pi, because what it means is your attempt to connect did not reach it.