Can anyone tell how to install Trilinos? Can xyce replace xschem?

Replacing xyce with xschem is not a proper statement. Xyce is just a circuit simulator and xschem is just a schematic creator. You create schematics on xschem and simulate them using xyce. So you have to use them both together.

the correct question is probably if Xyce can replace ngspice, and yes, they are both trasistor level simulators. If one or the other fails or takes too long you can fallback to the other. The goal is to have the sky130pdk (and following ones) to be compatible with both.

I put some notes I made when building Xyce in the #reram channel; didn't realize the question was copied here, which is a more obvious place to post those notes. . .