Hardware replacement, Raspberry Pi or a used PC?

permacomputing tends to be much more about the software than the hardware.

Always get the four freedoms first https://www.gnu.org/philosophy/free-sw.en.html

I used a Pi 2 for a time as a daily driver when my laptop had caught fire and it was able to handle stuff without much difficulty, though internet browsing would significantly take it down, making it freeze and require I take a break before returning. I ended up using it with my old tablet and was able to get through an entire semester of college, mind you this was back in 2015. I would easily imagine that a Pi 4 could do enough for you, especially if you used it with a remote connection distro specifically, setting up a server that you would pull your desktop from for your classwork.

I also have several old PCs that I've restored and have used and found them able to do everything I need and sometimes can even do more with less. The old Dell Optiplex SFFs are still being used everywhere and being thrown out, and are easy to get parts for or upgrade up to make it a good daily driver or even a server, I got three of them that were being thrown out by a hospital a few years ago, the hospital throwing them out as a "it has been 3 years so we gotta upgrade" policy. I ended up getting parts and we have them in use at home.

Raspberry Pi s are awesome for when you need a computer that doesn't draw as much power or take up as much space as a regular PC - I've used them in arcade cabinets and as local web/dns servers. I'll probably use a spare I just pulled out of ewaste as a media server. But I don't think I'd use one as a daily driver (I tend to just clean up old laptops and use those).

The RPI is a much better server, even with a 4 you gotta struggle with it to get streaming video. If you have a lot of firefox tabs open right now, look elsewhere.

I don't know your computing needs but I would say that it will probably not be enough. I suggest a pc build with used pc parts, unless you require a very portable device. In that case yes, a raspberry pi 4 is a good choice or an older used device running debian like others mencioned

I would go for a Pi - it has a power draw that is tiny compared to used PCs from previous ages. It is likely that the difference is significant (e.g. 150 W vs. 5 W).

Power consumption is especially relevant for servers, less so for computers used for brief periods of time.

I’ve been down this road myself. The newer pi’s seem like they could handle being a daily driver depending on your resource needs (mine are small). I bet you could even acquire one used at this point. I ended up going with a laptop being discarded by the local school system. My plan is to use it til I can’t, then I’ll probably work on a pi battle station. There are some great videos out there of people using the pi as a daily use pc, with success. Still I suppose it depends on your needs.

Always go used or something you already have available. Used phone also can work but the device itself is not really amenable to fixing. However, fixing is better than throwing out. The biggest thing is getting software to work on the damn thing.

Used > new tech. The others are on point.

It's not us single consumers doing a difference, and sometimes you need a little bit more flexibility these days. How do your daily needs change the equation? A more recent used PC? Business laptop? This could also point towards the Pi, if you like fiddling and experiments.

This goes slightly off-topic, sorry, but I'm throwing in shared computer resources. A tiny PC plus a community/non-profit data centre with virtual machines helping with our work load/gaming/...this could be sweet permacomputing, right?

There are some good second-hand Chromebooks that can be revived by installing Linux on them.

In general, refurbished enterprise Laptops are probably the cheapest with the highest quality. Those older Thinkbooks are nearly indestructible.