Anyone can replace a showerhead in 5 minutes. The only reasons someone would complain about showering with a crappy showerhead is either because they're staying in a hotel (although most hotels don't even tolerate that shit), or because they're a complainer. Just don't be the dweeb who uses teflon tape.
Replacing it isn’t the problem, buying it is. Yes I’m sure you can find showerheads with illegal flow rates available online, but reputable stores won’t sell anything over 2.5 gpm anywhere in the US, and over 2.0 or 1.8 in the states that have those limits. Amazon won’t ship the higher flow rates into a lower flow rate state.
Amazon does, however, ship showerheads that come with an instruction sheet for how to remove the flow restrictor. (One must only do this to compensate for one's home having low water pressure, of course.)
Note that a restriction on commercial sales still does not make an item itself "illegal".
I'm not trying to ignore the frustrating activation energy of having to spec/get/install your own showerhead rather than automatically having a default you like. But it's clear that amount of market friction here is much less than say, the overt digital authoritarianism currently going on across the whole phone app/software market. And it's important to keep this perspective, lest memes about "illegal showerheads" morph into groupthink that supports different authoritarian movements.
Teflon tape is for NPT (National Pipe Taper), which seals through thread interference. For the various things I do, I generally use a three layer sandwich of pipedope-tape-pipedope for the least chance of dealing with leaks. I'd rather take a little more time to make up a joint than have to disassemble and remake one in the middle of an assembly.
Showerheads are generally NPS (National Pipe Straight) which seals with a rubber washer. So if there is leaking, the real problem is that rubber washer is missing or old, or the female piece is cracked. Adding tape often encourages cracking the showerhead female, as it pushes out on the threads and showerheads are often chromed plastic. This goes doubly when the pipe coming out of the wall is actually NPT, and the tape encourages you to really over tighten it. Tape can be useful sometimes to hackily make things better, it's just not a good default.
Just make sure there is an indeed a rubber washer for the sealing. And if it leaks, try replacing that or even adding a second one first. Although none of this applies if both threads do indeed look tapered. And also the rubber washer often has a built in screen in the middle, to catch pieces of whatever (like bits of teflon tape, lol) rather than them clogging up the showerhead's holes.
