@User A follow up: if I change the transistor line in the example in "test" to:

X1 3 2 0 0 sky130_fd_pr__nfet_01v8 l=1u w=5u

So I add a custom length and width, the simulation also fails with "could not find a valid modelname". Conversely, my example doesn't result in an error if I remove the length and width parameters. Weird. How am I supposed to specify the transistor length and width?