* IPv6. A genuinely useful tool, in particular for homelabs: multiple globally routable addresses per machine. One address per service. No need for Host/SNI vhosting. Works well with containers. To get v6 support, either find ISPs/SIMs that do v6, or wireguard to a VM that providss a /56.

* SSH ForcedCommand. Lots of usecases here, for backups, file storage, git, etc.

* Verilog as a tool for software developers to learn digital electronics. VCS/code/simulation/unit tests are all a lot more familiar and expected for developers.

* Writing tools yourself. There's often decent stable libraries that do 90% of what you want, and the remaining 10% is less effort than dealing with awkward integration with off-the-shelf tools. This relies on having low overhead packaging/deployment, e.g. Nix/Guix/Bazel.