Not true. The DMCA makes it illegal to "circumvent" DRM schemes. It's also illegal to carrier-unlock your phone without your carrier's permission.
But even if these legal restrictions were to vanish tomorrow, we'd still be stuck with a similar landscape - most manufacturer control comes from technical restrictions combined with a high rate of churn so even if someone invests the time to figure something out, it quickly becomes yesterday's model. Fundamentally, understanding is more difficult than creation.
The calculus could be different on tractors, which are meant to last a real long time. Except the topic here too is focused on getting companies to positively supply things to help, rather than removing laws that hinder (FTA: "The agreement creates a mechanism to address farmers’ concerns and give them access to resources needed to repair their own equipment, such as diagnostic and repair codes, manuals and product guides.")
So my ultimate point is that you need to move past thinking that a Constitutional "right to repair" law would address these problems. Such a thing would be as ineffectual as the Constitutional "freedom of speech" has been in addressing the social media oligopoly.
Slightly OT, they pronounce router “rowter” over here, presumably to avoid the same issue.
On the plus side for Australia, we never have to hear the classic form:
> Rooter? I hardly even know 'er!
You could argue that any changes to the software are then the fault of the user, which is a reasonable point of view. But what if someone comes up with a mod that makes your wifi better by breaking transmit power rules (at the expense of others). Lots of people might use it, and then there are resulting widespread interference problems. Difficult to identify culprits, possibly too many to prosecute etc.
This already exists in multiple forms. It's incredibly easy to import adapters and antennas that give you an order of magnitude more power than you're legally allowed to use. I used one of those setups in high school to run uTorrent over the AP of the McDonald's half a mile away.
Regular folks don't care enough to break the rules.
In the past, most of the key aspects of the radio were pretty fixed in the hardware. Whereas now, more and more of the radio is in software (and/or FPGA), or at least configurable from software. Tinkering in that case requires a "per person" level of skill. Whereas tinkering with software requires one person to be able to tinker, and then lots of people can use the result.