I do not know the issue or solution for this, but here is a workaround I used.
Essentially, you will need to create the publish folder and file profiles manually.
I did this for a .NET Core 3.1 Blazor project
Step 1 - In your project, go to the Properties folder where you should find your launchSettings.json
Step 2 - Inside, create a folder and name it "PublishProfiles"
Step 3 - Inside of the PublishProfiles folder, create a file and name it "FolderProfile.pubxml"
Step 4 - Inside of this file, paste this code and add the location path to the folder you which to publish:
<?xml version="1.0" encoding="utf-8"?>
<!-- https://go.microsoft.com/fwlink/?LinkID=208121.
-->
<Project ToolsVersion="4.0"
xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<DeleteExistingFiles>True</DeleteExistingFiles>
<ExcludeApp_Data>False</ExcludeApp_Data>
<LaunchSiteAfterPublish>True</LaunchSiteAfterPublish>
<LastUsedBuildConfiguration>Release</LastUsedBuildConfiguration>
<LastUsedPlatform>Any CPU</LastUsedPlatform>
<PublishProvider>FileSystem</PublishProvider>
<PublishUrl>Your location path where you want to publish your application</PublishUrl>
<WebPublishMethod>FileSystem</WebPublishMethod>
<SiteUrlToLaunchAfterPublish />
<TargetFramework>netcoreapp3.1</TargetFramework>
<ProjectGuid>08d93ba4-c83c-47e9-a83e-73f12d97626a</ProjectGuid>
<SelfContained>false</SelfContained>
</PropertyGroup>
</Project>
Step 5 - Create another file and name it "FolderProfile.pubxml.user" and paste this code inside. Again, insert the path to your desired folder:
<?xml version="1.0" encoding="utf-8"?>
<!-- https://go.microsoft.com/fwlink/?LinkID=208121.
-->
<Project ToolsVersion="4.0"
xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<_PublishTargetUrl>Your location path where you want to publish your application</_PublishTargetUrl>
<History>True|2021-07-02T16:47:41.7255934Z;True|2021-07-02T12:44:24.1064885-04:00;True|2021-05-21T09:22:02.2383330-04:00;True|2021-05-20T17:42:40.0758569-04:00;True|2021-05-20T09:45:45.4390896-04:00;True|2021-05-20T09:02:32.8340404-04:00;</History>
</PropertyGroup>
</Project>
Step 6 - After this, you should be able to right click your project in Visual Studio, click the option Publish... and the screen with the Publish button should be visible.