Those old clients can have security advantages. For example, my MPC7400 processor is immune to meltdown and spectre. It also isn't supported by a typical javascript JIT, so that wipes out lots of other potential exploits. I'm pretty sure the RAM is old enough to be immune to rowhammer; it is PC133 in slots specified for PC100.
The web browser is of course obsolete. Newer ones run slower, take more RAM than the 512 MiB that the system has, expect a GPU, and have lots of dependencies.
The web browser is of course obsolete. Newer ones run slower, take more RAM than the 512 MiB that the system has, expect a GPU, and have lots of dependencies.