I just tried using LWC on my local, but not able to use
<lightning-input />. Is it available for open source? Is there any way to bring prebuilt lightning web components with
lightning namespace to local?
Currently no - none of the platform base component are available for off platform usage. Salesforce is targeting to open Source them in late July (#safeharbor) but their api / shape may also be slightly different than the known one due to missing Salesforce Service - will we see
For the 2nd Question - the only way as of today to use existing base components outside the platform would be via Lightning Out which is a different approach. I would wait those couple of months to see how its evolve with the LWC Framework
Yes, in a way they are available, checkout this npm to use base lightning component in your OSS LWC. Base Lightning Components
Also check this comment for details of how to get it installed