Nice to Inglais Santiago de Compostela trail??

The Renfe site shows two daily trains from Madrid’s Chamartín station to Ferrol. Alvia 04095 departs at 08:00 arriving at 13:12pm, while the Alvia 04175 departs at 17:45 arriving at 23:23. Both have stops en route. There are also two daily trains from Santiago de Compostela to Ferrol. Alvia 04095 departs Santiago at 11:22 arriving at 13:12. Alvia 04175 departs Santiago at 21:31 arriving in Ferrol at 23:23. Since you’re looking at 2023, train numbers and times will probably change, but for now you simply need to know trains to Ferrol exist. You could also fly into A Coruña, but would still need to get to Ferrol by train, bus, or rental car. It’s only 37 minutes away.

You could also ask your question on one of the many Camino forums or Facebook groups.

Any way you cut it, getting from Nice to Ferrol will be a pilgrimage of its own. But flying is the only truly reasonable option. From Nice or Marseilles. Perhaps through MAD or BCN. Then bus or train- take your pick.

Look on Rome2Rio to see some of the options. The bus system in Spain is pretty extensive.
As already recommended, check either some Camino FB groups or this website forum: https://www.caminodesantiago.me/
This forum that I posted the link to, has helped me immensely on all of my Caminos.

You could either fly from Nice to Santiago (or A Coruña, fewer flights though) through Madrid, or just fly to Madrid and take the late afternoon train from Madrid Chamartín. Option 2 takes longer but is a bit smoother because you do not need to coordinate with buses at the Galicia airports.