First off, what is best is subjective to each developer although when a decent starter project is presented on say GitHub one can tell if the code is good or not by how many stars a repository has. Then this is still subjective to skill level of a developer, if there is a good starter project that is above the skill level of a set of developer this can keep a repository from obtaining a higher rating.
My recommendation is to browse through the following list, inspect the code online, if the repository appears good to you, download and try it out. Or go and try out the following starter kit (the Use this template button will fork the repo to your account) which is based on .net5.
Also, consider using a third party Framework such as Telerik DevCraft which is an amazing set of tools and libraries. The libraries will take time to learn but well worth it. I've used these libraries in two different companies building SPA to Razor page solutions.