There are many old / obscure / indie RPG systems, not available off the shelf, not easy to find. Or easy to find as a pirated version. Would asking how to get a legal access to specific system be on topic here? I suspect not, but I thought I'll ask.
No, for a variety of reasons
I don't consider it a shopping question. Shopping questions are a common nickname for recommendation questions (read more in this meta post here) and since you already know which system you want to play, it isn't that anymore. However, it does suffer from the same problems and then some:
There's no best answer
For many systems, there's a clear single place to get it legally --- usually it's the author's site. But sometimes, that isn't the case and you have to start ranking between shops that stock the game.
Given two answers which link to different shops, which is better? The cheaper one? The one that has a history of delivering quickly? The one that gifts their profits to fight climate change? Ranking answers would be opinion-based, not to mention another problem:
Time-proofing is impossible
Shops go down or stop stocking the particular game you want. Answers would have to account for this, but it's unfeasible and we generally want to avoid questions that force the answers to do this.
It's an unbounded list question
With an unbounded number of answers whenever someone finds a new shop, it's definitely an unbounded list question and therefore off-topic.
It can be hard to know what's legal
Consider a system that's hard enough to find legally that asking the Stack is a better strategy than googling. Such a system might not have a homesite or other clear trail left online. Suppose someone posts a download link to it --- how should the users of the Stack know whether the link is legal or illegal? Shops aren't exempt either --- I would maybe trust larger RPG retailers not to risk their reputation peddling pirated content, but there's no simple way to draw the line.
No, it's a shopping question
Unfortunately, that would definitely fall under Shopping Questions which are currently off-topic.
But you can definitely hop into chat and there you might find someone who knows where to find those RPGs.
That would be a shopping question (a recommendation for suppliers of games, rather than for which game) and/or list question, making it off topic.
It would probably also be a duplicate of Where can I buy original edition and out-of-print roleplaying books and accessories?, which was indeed closed as a list question.