> I'm thinking of building a text-annotation based app _alone in my spare time_. The core usage loop is about viewing and interacting with "visual markup" applied to a body of text. So lots of tooltips/hoverbars I guess.
Can you elaborate a bit more on this part, please? Or show us a mockup... doesn't have to be anything fancy, just like a pen and paper sketch or a simple Figma.
I'm asking because it kinda sounds like you're wanting to do something like an online IDE or Google Docs, where you're manipulating a body of text in the style of a rich text editor. If that's the case, it's possible the HTML DOM model isn't quite the right fit for you... you may find it better to abstract over a Canvas or WebGL object instead of trying to shoehorn that experience into the raw DOM. That way you have full control over rendering, outside of the normal layout/styling/rendering loop. It might also make a good case for a single-page app (at least the majority of the editor itself would be, and the other stuff -- marketing, blog, etc. -- can be routed to individual pages).
In that case, it wouldn't be so much a question of "framework" in the sense of React, Vue, etc., which traditionally work on the DOM. It might be more a question of "engine", like whether to use something like PixiJS to manipulate the graphics layer vs rolling your own. State management can be done with something like Redux (even without React), or if you choose to use a frontend framework for the rest of it, you can maybe use their state solution with your rendering engine.
In addition to choosing a low-level graphics lib, you can also look at some existing rich text markup solutions. A CMS I used had a good blog post on this: https://www.datocms.com/docs/structured-text/dast (especially the parts of about "abstract syntax trees"), along with their open-source editor: https://github.com/datocms/structured-text
That's one possible to way to deal with complex annotated text.
A more widespread one is the toast UI editor: https://ui.toast.com/tui-editor
I know you're not just working in Markdown, but these give you an idea of what it's like to work with complex text trees in JS.
Once you have the actual text editor part figured out, choosing the wrapper around it (again, just for marketing pages, etc.) is relatively trivial compared to the difficulty of your editor app. I really like Next.js myself (if you choose React), but I don't think you could really go wrong with any of the major choices today... React/Vue/Svelte/etc. And it looks to me like the complexity of your site wouldn't really be around that anyway, but the editor portion.
Lastly: I don't think ANY JS tool or package is going to be maintained in 10 years. Frankly, 2 years is a long time in the JS ecosystem :( I'm not defending this phenomenon, I hate it too, but that's the reality of it. If long-term maintenance is a goal of yours, you might want to consider writing abstraction layers over third-party tools you use, so you can easily swap them out when future things come out (because they will). The web itself is changing too fast for libraries to keep up; instead, people just write new ones every few years. An example of this is the pathway from the Canvas to WebGL to workers to WASM (and how to juggle heavy computational vs rendering loops around)... a lot of the old Canvas-based renderers, which were super powerful in their time, are now too slow vs the modern alternatives. Nobody is going to port the old stuff over, they just make new libs. It's likely that trend will continue in the JS world (that whatever you write today will be obsoleted by a new web API in a few years).
Lastly, as an aside, TypeScript is a superset of JS... if you find a JS project/lib/plugin that you want to use, there will often be types for it made by the community (https://github.com/DefinitelyTyped/DefinitelyTyped) , or you can write your own types for it. I don't really have an opinion about TypeScript vs writing in some other language and compiling to JS, but it would probably be easier to find help (especially frontend) in the future if you stick with TypeScript instead of convoluting your stack with multiple languages. Sounds like most of your app will be clientside anyway with limited backend needs.
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Tech aside... have you considered partnering with a frontend dev for this? I know you said "alone", but just having someone set up the basic skeleton of such an app with you for the first month or two could be super helpful. Or a UX person to help you with some of the interactions before you start serious coding. They don't have to be with you the whole journey, but maybe they can help jumpstart your project so you can then work on adding features & polish in your spare time, instead of figuring out basic architecture? Unless, of course, that's the part you actually enjoy. In that case, don't let anyone rob of you that :)
Have fun! Sounds like a cool project.