Qucs-S is a circuit simulation program based on Qucs circuit
simulator.The "S" letter indicates SPICE. The purpose of the Qucs-S
project is to use free circuit simulation kernels (Ngspice, Qucsator,
Xyce) with the unified GUI based on Qt6 toolkit. It merges the
power of SPICE and the simplicity of the Qucs GUI. Qucs-S is not
a simulator by itself, but it requires to use an external simulation
backend with it. Qucs-S allows to use the following open-source
simulation kernels:

    -Ngspice is recommended to use. Ngspice is powerful
    mixed-level/mixed-signal circuit simulator. Not included in
    wip/qucs-s pakage. Available in cad/ng-spice package.

    -QucsatorRF for RF and microwave circuits design. It provides
    advanced models for such devices microstrip lines and waveguides.
    QucsatorRF is not SPICE compatible. Included in wip/qucs-s
    package.

    -XYCE and SpiceOpus are other simulators that can be used from
    QUCS-S. Not included in wip/qucs-s package.


See the https://ra3xdh.github.io/ for more details.
