I recently migrated the Dotnet Foundation website, https://dotnetfoundation.org/ to ASP.NET Core 3.0. The site was initially built on ASP.NET Core 2.1 and I found this as a good learning opportunity.
Read more: https://ankitvijay.net/2019/10/21/migrating-dotnet-foundation-website-to-asp-net-core-3-0/