As to Kobe Bryant, yes his helicopter flew into terrain (unsurprisingly, 'flew into terrain' is incredibly common in aircraft accidents. Sadly, most of them are perfectly serviceable when they do so). There is no indication that the issue was a radar altimeter (if one was even installed, I don't believe they're required in that class), much less one that was being interfered with. I don't think the NTSB report is out yet, but I expect the cause will be what it commonly is: a pilot (with a famous and rich client who wanted to get somewhere quickly) taking their vehicle into marginal weather conditions beyond what they and their aircraft are competent to handle. Working on that problem will save a hell of a lot more lives than investigating 'may be a problem' that no one can even describe a mechanism for.
Existing synthetic vision systems would have easily prevented this. They're not even that expensive - built in systems can be had for a few tens of thousands of dollars, or non-certified iPad based systems for a few hundred.
That crash was likely due to disorientation in dense fog with an experienced, IFR rated pilot but who didn't experience much fog in LA. A radar altimeter would have been unlikely to help.
Just this year Kobe Bryant died because his helicopter impacted the terrain.
If this happened after the sale, you'd have to do just as difficult of an analysis to prove that 5G frequencies did not play a role in the impact, so why not do the analysis before hand?