Thank you. I've had to move on to something else for now, but will try to return to this and get it sorted.
Just a couple quick comments.
I don't use classes anymore. I use function components for everything. Have you tried function components so you can also use hooks, etc?
Also, as far as I can tell, react-scripts-ts is not the recommended way to use TypeScript in React. Have you tried a local example (not StackBlitz) following the suggestion here:
https://create-react-app.dev/docs/adding-typescript/
? To really compare, I would need to see your tsconfig.json at least.
I have code that was running fine on v18.3, but gives the error included in my first comment on v18.4 and the only change is the upgrade of v18.3 -> v18.4.
But, as mentioned, my code uses function components and the recommended way to use TypeScript with CRA.