Linux on a Mid 2007 iMac

We have a 24 inch Mid 2007 iMac in our living room that is clearly showing its age, but still working OK enough (albeit slow) as a TV (SD channels on DVB-C via USB stick), DVD player, and Web streaming station. The machine is stuck on macOS El Capitan (OS X version 10.11.6) and doesn't get updates anymore. I was wondering if putting Linux on it might help.

I ended up installing Xubuntu 18.04 (64 bit), mainly because it uses the lightweight Xfce window manager. For some reason USB boot never worked (the same USB pen booted on a MacBook Air just fine), so I went and, in 2018, bought some DVD+RWs (probably the last time I ever do this) and it booted.

Pros

All hardware was immediately recognized and ready to go, including the (proprietary) Wi-Fi drivers, the multimedia keys on the iMac keyboard, the mouse wheel (I had to compile a kernel back in Debian 2.0. Hamm times), and even the USB TV stick (Hauppauge 930C, I needed to copy its firmware file to /lib/firmwares). The system overall boots a lot faster (it's still a spinning HDD and still only has 2GB of RAM) and, once up, feels really snappy again (Firefox Quantum is a lot faster than Chrome Beta to start, though). Dual boot works fine, everyone recommends rEFInd, so I just went with that.

Cons

The system still doesn't decode HD DVB-C channels smoothly (it does now, see the update below), despite being on only ~25% CPU load (compared to 99% on macOS where it works neither). If there's someone from Linux TV reading along, I'd love to talk to you. I don't particularly like Gnome Software that Xubuntu ships with instead of Ubunutu Software Center, but I fixed this by installing the Synaptic Package Manager.

2018. The year of the Linux desktop :-)

Update

I learned about the VDR project yesterday, and after some fiddling now have HD DVB-C TV on Xubuntu, something that never even worked on macOS. The setup was super involved and old-school Linux, but thanks a ton to the Debian folks for the helpful instructions to install VDR.