I have been running Ubuntu on my mid-2009 15" MBP for some time and it runs fine. This MBP was retired as my main MBP in 2014 when I purchased a new model. My primary reason for switching to Linux on the 2009 MPB is because it can't run macOS Sierra and it does not run anything past Mountain Lion very well. Even with 8GB of memory install. I've had 8GB installed in it since 2011. In fact, the best macOS it runs is Snow Leopard...problem is Snow Leopard is no longer supported by Apple, Google, Mozilla...so I did some research and found Ubuntu and the Ubuntu MacBookPro community to be very helpful. I started out with Ubuntu Desktop 14.01 and am currently running Ubuntu Desktop 16.04.3. Nearly all the hardware features work...WIFI, backlit keyboard, temp sensors, etc. Don't get me wrong, I love macOS. My 2014 15" Retina Display is running High Sierra just fine. I have VMWare Fusion 10 installed on it and run several different VMs on it just fine. But I wanted to breath new life into my 2009 machine and Ubuntu has delivered nicely. Burn a copy of the Ubuntu ISO onto a USB drive using Unetbootin (
http://unetbootin.org/), boot up the old MBP from that USB, run the install. Then use this page as a reference for what needs to be installed to enable all the hardware features like WIFI, backlit keyboard, etc:
https://help.ubuntu.com/community/MacBookPro Take your time to do your research and don't rush through the process. I think you'll be pleased with the results and this will breath new life into older but still very solid hardware. Enjoy!