I have recently pulled out my late 2008 unibody macbook, upgraded the RAM and put elementary OS on a new SSD.

The issue
I can't safely put the computer into sleep or suspend mode, because whether I trigger it myself or it goes there itself, I can't wake the machine with a key press, USB mouse, trackpad. I have to force a restart with the power button, often requiring a long hold to get it to do anything.

About the Machine
It's an Apple Macbook- 5,1.
Intel Core 2 Duo processor.
Graphics card is C79 GeForce 9400M NVIDIA
Samsung 500GB SSD.

uname -v
#53~18.04.1-Ubuntu SMP Thu Jun 4 14:58:26 UTC 2020

The issue seems to be the same whether I use the built in graphics driver, or with NVIDIA's driver.

While I've been playing with linux for a while now, this is my first serious toe-dip back into the world of linux for many years. (Maternity leave means I had to give back my work laptop, so have resurrected this old macbook with a linux install, which is working quite well, apart from this annoying issue- if I'm going to be away from the machine for a while I have to close everything and shut down!)

Have googled this issue, can't find anything too specific, and would appreciate some explanation of what different commands do, rather than "install this utility" or "run this command"

UPDATE: I switched on my computer, but didn't log in straight away, and it was able to resume to the lock screen. Weird.

Consider using Debian Buster on your Macbook. I don't use Macbooks myself but Debian will be the best solution. As far as I can tell these models use 32-bit UEFI bios so be prepared to try the 32-bit version. Debian Buster comes with 5 years support ends in 2024. You will need the i386 architecture for the 32-bit version. If you opt for the 64-bit version use the amd64 architecture.

Having similar problems with a 2009 MacBook Pro. Using nvidia's driver. When suspending from the power menu or by closing the lid, the computer won't wake up after. However, weirdly, it seems to wake up just fine using pm-suspend from the command line.

After "investigating", it appears that the laptop *is* waking from suspend - the lock screen is just not showing up for some reason. Pressing Ctrl-Alt-F7 shows the "this session is locked, you'll be redirected..." screen, then nothing.
Do you think using another distro, or somehow changing the login screen would solve the problem?

This might be a bit off topic but I'm running the same exact OS on the same exact computer what a coincidence! AND I also upgraded my ssd too! I also have the same exact specs. Wow!

I'm running Fedora on this 2011 MBP maybe give it a try if it's still giving you troubles.