There are many Raspberry Pis on the International Space Station (AstroPis). They're subject to a similar amount of space radiation as CubeSats in LEO, and they work just fine. There's also an increasing trend of building CubeSat On-Board Computers (OBCs) as some form of Linux System-on-Module (these would traditionally be microcontrollers). I think Raspberry Pis (especially the Compute Modules) are quite suitable for Payload Data Handling (PDH) systems, although I've personally not had a chance to launch a RPi chip yet.

In my experience, having provided advice to a lot of academic CubeSats: the issues usually aren't related to the parts, the problems are usually lack of testing and general inexperience.

Yes, a Raspberry Pi isn't radiation hardened, but in LEO (say around 400-500 km) the radiation environment isn't that severe. Total ionizing dose is not a problem. High energy particles causing single event effects are an issue, but these can be addressed with design mitigations: a window watchdog timer to reset the Pi, multiple copies of flight software on different flash ICs to switch between if one copy is corrupted, latchup detection circuits, etc. None of these mitigations require expensive space qualified hardware to reasonably address.

The usual issues I see in academic CubeSats are mostly programmatic. These things are usually built by students, and generally speaking a CubeSat project is just a bit too long (3-4 years design and build + 1-2 years operations) to have good continuity of personnel, you usually have nobody left at the end there since the beginning except the principal investigator and maybe a couple PhD students.

And since everyone is very green (for many students, this is their first serious multidisciplinary development effort) people are bound to make mistakes. Now, that's a good thing, the whole point is learning. The problem is that extensive testing is usually neglected on academic CubeSats, either because of time pressure to meet a launch date or the team simply doesn't know how to test effectively. So, they'll launch it, and it'll be DOA on orbit since nobody did a fully integrated test campaign.