Yeah, there are retrocomputing hobbyists who mess around with sometimes-physically-large computers that were important many decades ago. I don't know if anyone is hacking on vacuum tubes of the kind that you could in principle build a computer with - there's a reason they became obsolete for digital computation almost as soon as the transistor was invented. On the other hand, I personally think it would be neat to try to build a CRT in a garage, which is of course a type of vacuum tube. I don't think this would be an easy garage project, but it does seem like might be tractable for someone who understand physical manufacturing and electronics well, has access to glassblowing equipment, etc.