Dahomey.Json VS aspnetskeleton2

I'd add that there are some libs that enables features of Newtonsoft.Json for STJ. E.g. this one is pretty exhaustive.

There's another sample project which demonstrates how to set up the latter strategy. (In this case the TS compiler configuration is included in the csproj but, of course, you can use tsconfig.json as well. For that, here's another example.)

It's not at all. For more complex applications (which benefits from a service layer) I use exactly this architecture you described. I've built a few applications with it and it worked fine for me. If you want to take a closer look, I also have a template for this. (Haven't had the time for documentation yet but it can still give you some ideas.)

Table rendering logic (implemented as global razor helpers)

As for TypeScript, you're kinda out of luck because the TS compiler is written in TS, so it inevitably needs a JS runtime (like node) to run. However, IMO it's strongly advisable to use TS for any client-side logic bigger than 100-200 lines of code. So regarding this I usually just accept the compromise. At least, the following setup works for me perfectly: I configure the TS compiler to emit ES6 modules and I bundle the emitted JS modules using the lib. You can find a working example of this in my web project template: tsconfig.json, bundler configuration.

I use this code generation strategy combined with .NET Core Local Tools to generate boilerplate code (2-3 source files at specific locations) for CQS commands and queries and I'm quite satisfied with this method so far. You can check out the sources of my codegen tool here if you want to explore it. Might give you some ideas.

But TBH the only feature I really missed when I work with STJ is polymorphism support. You don't even need a 3rd party lib for that: it requires some gymnastics but it can be implemented relatively easily by creating a custom JsonConverterFactory + JsonConverter. This implementation of mine can give you some ideas. (Also does type whitelisting based on Protobuf configuration.)