Vanilla generated project from this template does not compile.

[nils-a]

The first error that I encounter is

error MSB3823: Non-string resources require the property GenerateResourceUsePreserializedResources to be set to true. [...\src\GitExtensions.PluginTemplate\GitExtensions.PluginTemplate.csproj]

[nils-a]

When I add <GenerateResourceUsePreserializedResources>true</GenerateResourceUsePreserializedResources >, the next error is:

error MSB3822: Non-string resources require the System.Resources.Extensions assembly at runtime, but it was not found in this project's references [...\src\GitExtensions.PluginTemplate\GitExtensions.PluginTemplate.csproj]

[nils-a]

When I add the missing reference, the next error is:

warning MSB3245: Could not resolve this reference. Could not locate the assembly "ResourceManager". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. [...\src\GitExtensions.PluginTemplate\GitExtensions.PluginTemplate.csproj]

error CS0246: The type or namespace name 'GitUIPluginInterfaces' could not be found (are you missing a using directive or an assembly reference?) [...\src\GitExtensions.PluginTemplate\GitExtensions.PluginTemplate.csproj]

Essentially, the references from the downloaded GitExtensions are not found.
This was actually fixed in gitextensions/gitextensions.extensibility@437aacb, but that code is currently not available in a released version.

[nils-a]

When GitExtensionsPath is corrected, the next error is:

error CS0012: The type 'Image' is defined in an assembly that is not referenced. 
You must add a reference to assembly 'System.Drawing.Common, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.  [...\src\GitExtensions.PluginTemplate\GitExtensions.PluginTemplate.csproj]

[RussKie]

What exactly are you trying to build and what are the steps?

[nils-a]

I created a repo from this template and build it using dotnet build GitExtensions.PluginTemplate.sln

[RussKie]

The template appears to be still targeting net461, so that'd certainly explain the issues you're observing.
Please have a look at https://github.com/gitextensions/GitExtensions.GerritPlugin - that's probably the most actively developed plugin I'm aware of - that should be give you ideas what tweaks required.