In 2019 I did SJPdP to León, then the Salvador to Oviedo. However, rather than the Primitivo, I walked to Avilés and continued on the Camino del Norte, because I had had to abandon it due to injury the year before. I wanted to finish the Norte. Hopefully, my next Camino will be the Norte/Primitivo combo.
As far as the Camino del Salvador goes, as you probably know, there are usually very few pilgrims on it. But there are enough albergues - just not too many places to stop and eat between stages. Some albergues ask that you phone them the day before to let them know that you are coming.
@Elle Bieling's website is a good resource.
The Camino de San Salvador is perhaps the most mountainous of all the Caminos de Santiago. This short but spectacular, pilgrimage path of only 119 kilometers (74 miles), figures by my GPS tracks, will physically test most of you! Do not be fooled by the short length.
www.pilgrimagetraveler.com