The backend of this web server runs the original R implementation of the GMYC model authored by Tomochika Fujisawa and Tim Barraclough. To run the R GMYC locally, please check Tomochika Fujisawa's blog. There is also a python implementation of the single threshold GMYC model in my GitHub repository, and a Bayesian implementation of the single threshold GMYC in R by Noah M. Reid.
I encourage you to try both GMYC and PTP model on your data. They are based on quite different models, but if they give you similar delimitations, you can be more confident on the results.