It's been around two decades since I last did an LFS install, but I still find the knowledge I gained to be useful to understanding how boot loaders, the kernel, init systems, etc. work today—not just bare metal and VMs, but also in containerized environments.
Same, I'm closing in on twenty years since I did it on a Pentium 2 (which took a very long time to compile). But in a matter of weeks I had my own linux router that I built from scratch.
I was too much of a novice to completely understand everything I did but over time the puzzle pieces fit together and I realized it was just about the most solid foundation I could have engaged in. I'd suggest it to anyone that interacts with Linux and the time requirement to compile everything is far, far less than it was years back.
I spent a couple weeks planning a LFS install about 20 years ago. I then didn't have time to look at it all for about year, so I never went through with it. But I still learned a lot just documenting all steps and preparing with the worse case of not having decent internet if something went wrong.
Same. Any time I'm asked a question like "How can I better understand Linux?" by someone new, I tell the person asking to do LFS and to take the time to understand it. Even some long-time system admins and software devs would benefit greatly.
