But looking at the installation instructions[1], I can't help but think that their reluctance to use Docker feels contrarian for no reason (and the quip about it being "out of fashion" completely misguided). This whole procedure could be automated in a Dockerfile, and actually running uMon would be vastly simplified. Docker itself is not much more than a wrapper around Linux primitives, and if they dislike it specifically for e.g. having to run a server and run containers as root, there are plenty of other lighterweight container alternatives.
There's an argument to be made that the "Simple" Network Management Protocol they're a fan of is far from being simple either[2]. Configuring the security features of v3 is not a simple task, and entire books have been written about SNMP as well. They conveniently ignore this by using v2c and making access public, which might not be acceptable in real-world deployments.
I'm all for choosing "simple" tools and stacks over "complex" ones, for whatever definition of those terms one chooses to use, and I strive to do that in my own projects whenever possible, but simplicity is not an inherent property of old and battle-tested technologies. We should be careful to not be biased for technology we happen to be familiar with, but be pragmatic about picking the right tool for the job that fits our requirements, regardless of its age or familiarity.
[1]: https://tomscii.sig7.se/umon/#Installation%20and%20getting%2...
[2]: I have a pet peeve about tools or protocols with "simple" or "trivial" in their name. They almost always end up being the opposite of that as they mature, and the name becomes an alluring mirage tricking you into its abyss of hidden complexity. I'm looking at you SMTP, TFTP...