I have experimented a lot with my Raspberry Pi over the years since I got it. Mostly, however, it has spent its time collecting dust in the wardrobe, because I always run into show-stopping issues every time I try to actually use it for anything.
In every case so far, I've not got to boot it up with a USB stick containing a standard installer, as one would install an OS on an x86 machine these days (previously from CD-ROMs DVD-ROMs). Instead, I've been handed an ISO which I then have to use special software to "burn" directly onto the "hard disk" of the RPI -- the flash memory card, that is, which is then put into the RPI and booted up.
This "convenient" way of installing the OS for the RPI has at least one serious issue: you never get a way to enable encryption, because there is no installer where that would be picked.
Instead, I was forced to spend endless hours trying to figure out how to enable encryption after the fact. This sounds like it would be doable or even simple, but it's not. I don't care what anyone says: I'm a programmer and poweruser since childhood, long ago, having done all kinds of advanced things with computers, and I just couldn't figure it out. When online tutorials (frequently outdated or plain wrong) start talking about entering fixed numbers into long, error-prone manual commands, never explaining any of it properly, I can't help but "zone out" and sink back in my chair, killing the tab and forgetting about it.
I wasted quite a lot of time trying to use VeraCrypt, which I already use on Windows. However, it turned out that it actually does not support actually encrypting the disk on Linux! Only on Windows! I only realized this after plowing in many painful hours into trying that solution.
At this point, I have concluded that, whether on purpose or just for whatever other reason, enabling encryption after installation on Linux is just not doable. For me. Maybe it is for you, because you are much more intelligent than I, but it isn't for me. None of those guides help whatsoever. It's impossible in my context.
With this in mind, I'm trying to get a real installer for some Linux onto my Raspberry Pi. Is this available at all? Given the absence of such a thing whenever I've looked for it, I have to assume that there is a reason that this doesn't (seem to) exist.
Is it somehow not possible to have a real installer for the RPI? What prevents this technically? Why must the OS be "put onto" the flash card rather than "installed once booted up" from a real installer?