considering things such as job availability, salary, and ease of working in the ecosystem.
I've worked with Flask, Express, NextJS, and vanilla PHP professionally, and while they feel different in structure and ergonomics, they all do the same thing and the transition was easy.
As far as job prospects, my bet is on Rust/Actix. I'm pitching the idea of creating new micro-services with Actix to my company. (We're a Java shop). I implemented a simple proof-of-concept api server that takes in a single type of request, runs some business logic, makes a db call and returns a response with additional fields. Preliminary testing has shown that the Rust/Actix implementation is 5x faster at processing requests compared to the Java/Spring implementation.
With python/Django it is going to be easier to land a backend position, where you will be using Django mostly for building APIS and interacting with databases and third party systems and it will be less likely you will be expected to do frontend related stuff. Sadly not many companies nowadays do frontend with Django anymore, even if it were the right tool for the job, it is unfashionable to not do SPAs in most companies.
With node, it will be easier to land on a position where you're more "full stack" and expected to also know css, html and more frontendy stuff.
nodejs/javascript story is so fragmented, but there's a lot of innovation going on right now for how to make the most performant web app without sacrificing developer productivity.
These things do not depend much on the tech you learn. Besides, Django and Node.js are way too mainstream to notice any difference in salary/job offers.
> and ease of working in the ecosystem.
Pip is "less worse" than NPM in my opinion.
But, why don't you learn both? Is not that it's going to take you years to learn any of such frameworks.