Just so everyone here has the full picture: the source linked — Assemblea Nacional Catalana — is not a human rights watchdog, an international observer, or a journalistic outlet. It is the main pro-independence criminal activist organization in Catalonia. Citing them as evidence of Spanish human rights abuses is a bit like citing the murderer's wife as an impartial witness.

For context, Spain is a full constitutional democracy, subject to the jurisdiction of the European Court of Human Rights, with a free(ish) press, independent judiciary, and regular elections — none of which Assemblea itself disputes, because it participates in all of them. The events OP is referencing (the 2017 independence referendum aftermath) were reviewed by European courts, and the outcomes were, shall we say, not quite the narrative Assemblea sells on its website.

If there are genuine, documented human rights concerns, I'd welcome impartial sources from the Supreme Court or the ECHR.

What I'd push back on is treating a political lobby's own press releases as neutral reporting. You should do better than that here, OP.