Better still is to install some Linux on the machine which will make it useable for normal daily tasks. I'm typing this on a 'late 2009' 27" iMac running Debian, on longer train trips I'm using a 2011 Macbook Air also running Debian. No special browsers needed, just install Firefox.
One thing you have to keep in mind is that most of the Macs this browser targets use PowerPC processors, not Intel. The heyday of Linux on PowerPC Macs was around 15 years ago, and most of the support has rotted by now (i.e. you won't be able to run a mainstream distro or even get accelerated graphics). Additionally, by now most people who still keep PowerPC Macs around do so because they have software that will only run on an older version of Mac OS X, or even Mac OS 9 (Tiger was the last version of Mac OS X to have support for running Mac OS 9 software) so running Linux wouldn't be a good option for that reason.
Right, you can definitely do that on any core2duo or later 2008, 2009 vintage Mac. The first gen 2006 macbook pro intel and other 'core duo' from 2006 are 32-bit only so that really limits the x86 linux OS selection for modern use. And PowerPC platforms even less.
I had Xubuntu, Lubuntu on mentioned above eMac and frankly, it was awful - only OSX and OS9 were making that machine somehow usable. I had fun running that computer during mid-pandemic with all sorts of gems found in macintosh garden.