You seem to base this on lack of due process, however I've only heard of red flag laws that specifically require due process before a judge. Are there others? If so, it would be useful to distinguish them. Otherwise, the statement is generalization.
Due process is the baseline required to deprive someone of “life, liberty, or property.” If you could take guns away with merely due process, then you wouldn’t need the second amendment, because guns are also property. That right merited it’s own amendment, with additional protections.
Of course the Second Amendment is not unlimited, just like the First. My point simply is that due process, by itself, is not enough to take away the right. You need to be able to point to an inherent limitation of the concept of “the right to keep and bear arms.” As Judge Barrett points out, while the concept of the right to bear arms was not unlimited, it doesn’t necessarily exclude felons (and, as her sources show, “dangerous people” either). The New Hampshire proposed amendment, for example, would have excluded only people who had engaged in rebellion.
Given that the system requires a law to be passed before a challenge in court, this reasoning is inherently fallacious, since if it were true, no law could be ruled unconstitutional.
As far as the US system is concerned that means some forms of limits on the second amendment /are/ constitutional and the 2nd amendment is thus definitively not unlimited unless and until the court issues a ruling that contradicts the previous rulings.
Meaningful and lawful arms controls cannot exist in the US without a new amendment modifying the 2nd.
Then, the subject of the order must fight (at great expense) to regain their rights, which is a de facto presumption of guilt.
No hearing. No charges. No grand jury. No due process.
Due process might be a 30-day order to confiscate guns. If they can't get a grand jury indictment or involuntary commitment to a mental institution in those 30 days, the gun owner gets their guns back automatically and can't be subject to another red flag for 10 years.