Our first day in Sardinia, and cycle.travel threw us a few surprises on the route between Porto Torres and Algerho, with the back-road suggestions immediately being not as great as we have grown used to in Germany and France.

https://cycle.travel/map/journey/695073

The first small road between via points 1 and 2 was classed as paved: parts of it appeared to be an old Roman road with remnants of old stone paving, but it was a rough rock and gravel road for the 2km, narrowing to a walking track toward the end. It was a fun challenge on our gravel bikes, particularly after rain, forcing us to navigate some big puddles, but it would have been very difficult going on road bikes.

The section marked as unpaved at via point 3 was fine, except that the gate from the SP65 was marked private property. We risked it, and didn't meet anyone, so we cannot confirm how friendly the owners might be.

The biggest problem of the day was at via point 5, where there is an impassable locked gate (and google street view shows that this has been some sort of barrier since 2011). We needed to back-track and go around, which added a few km to our day. (The section between via points 4 and 5 are gravel, not sealed)

Otherwise, our first day's riding in Sardinia was pleasant and the other road suggestions were good!