I have an MINLP problem to solve where I was initially using 'ipopt' solver but the solution was not sticking to 'binary/boolean/integer' domain type for a variable. I am not sure which free solver would be good to go? Also, I understand 'SCIP' is not straight forward to use.
SCIP used to be a bit challenging to set up with PYOMO as we needed to build the ASL interface. It's been a few years so I don't know if that's changed, but you can find a relevant discussion here.
What might be easier would be to use Couenne, which is a deterministic global optimisation solver for MINLP and works out of the box with PYOMO.
If you are a student/academic, you can also use our own global MINLP solver (Octeract Engine) for free.
If you do, you can find a detailed tutorial on how to use it with PYOMO on Windows & Linux here.
You can use SCIP with PYOMO easily. My way is: At first, use an executable SCIP version, it is available for the 7.0 version. After then giving the path of the executable to PYOMO, such as:
solver = SolverFactory('scip', executable="./scip")
It works. But I use BONMIN in same way.