Suggesting such a hack would be illegal seems to be a bit of fearmongering.
The real issues with those hacks are:
1) you have no assurance that the manufacturer won't plug the respective hole in a future firmware update (which, if they're nasty, may also prevent you from going back to an older firmware version),
And yet, after a few years, they have done nothing to prevent the unlocking. They could change the encryption, heck, they could change it with every release. They have done nothing. Selling thousands a week is more important on low end models. At one time I watched TEquipment's inventory numbers and it appeared they alone were selling 1000+ per week.
2) for those who care about warranty: not only may the manufacturer refuse units that have been "hacked", but they may routinely update the firmware if you send in yours for repair, so it may come back with the hole plugged (see 1),
So? I would just 'unhack' the scope before sending it in and 'rehack' it when I get it back. Do you really think Rigol is unaware of this hacking? They know and they don't care. They also know commercial customers won't hack the scope and will likely pay the extra bucks for the official version. It is probably worth it to Rigol to get these scopes in the hands of hobbyists and hope for name recognition when the owners go to work and recommend their products.
I blew off the warranty when I replaced the fan and the selector switch. Somehow I just don't see the warranty as a big deal on a $350 scope. If it dies in a few years, I'll buy something else. I've had it a couple of years so my cost/year is about $175 and falling every day. If I get 10 years out of it my cost is $35 per year!
3) any feature that is not sold as in-the-field-upgradeable may simply not work reliably if you enable it through a hack.
That's the entire point of optional upgrades. I can choose to buy the feature long after I buy the scope. These unlocked options aren't some kind of 'hack' (I hate that word!) it is simply unlocking features already designed for field upgrade. They are already built into the scope. There's no 'hack' involved, it's simply 'unlocking'.
I think that Siglent SDS 1204X-E is quite the scope. I might ultimately upgrade from the DS1054Z but I don't think I'll be getting rid of it.
We shouldn't pretend that a $350 scope is a big deal. Keysight still makes $300,000 scopes so these entry models aren't even a wart on a real scope.
It really doesn't pay to take sides. The Rigol is rightly criticized for a poor UI, the Siglent is supposed to be a lot better. Siglent is criticized for very slow release of firmware upgrades (if any at all) but I don't know anything about that. Rigol has been good about firmware upgrades. Rigol has been criticized for fan noise. There is a fix but it blows the warranty. Rigol has been rightly criticized for the selector switch not having detents. Again, there is a fix that blows the warranty. The point is, both scopes have warts.
But I would always prefer more bandwidth and that SDS 1204 is probably my next scope. 200 MHz is greater than 100 MHz and it matters.