Finding a version of Linux that works isn't an issue. Finding a web browser that's usable on an old version of Linux, with today's web might be an issue. But that's not unique to Linux.
I have to believe he can find a Linux distro that would work, subject to whatever support limitations there were at the time (which could be pretty significant 20 years ago). But he may not be able to do much with it, including connecting to the network with any level of security.