@User: I have set up a bunch of test cases that will go into the PDK library; each netlist has the "best" include statement or statements for testing the device. I am generally annoyed at the complexity and deep hierarchy of the SkyWater device model files. On the one hand, using "sky130.lib.spice" is the "recommended" way and works for most (but not all) devices. On the other hand, it causes ngspice to spend about a quarter minute reading all of the files that get included, whether they're needed or not. But each level of the hierarchy defines some parameters and then includes more files, so if you miss any of them, you end up with undefined parameters and ngspice fails. So probably the best thing is just to use ".lib sky130.lib.spice <corner>" and put up with the quarter minute delay. But do note that there are specific devices for which even that will fail.