help understanding nested cross validation
Generally, you consider the outer CV as just estimating the performance of the method of fitting.  You don't expect a final model out at this point.  You can then apply the same method of fitting a model (what was happening in the inner CV) to the entire dataset to produce a model, and you say that you expect the performance estimate to apply to this new model.

https://stats.stackexchange.com/a/65158/232706
https://datascience.stackexchange.com/a/16856/55122
https://stats.stackexchange.com/q/11602/232706
https://stats.stackexchange.com/q/52274/232706