First the good news. You already know this, since you’ve walked it, but for others — With regard to ”well-marked,“ the Invierno is probably the best-marked route of any I have walked. Millions of euros have been spent on mojones and other markings. It may become “fairly popular” in the future, and I do think that the numbers are starting to rise, but on my last Invierno in 2019 I met one peregrino in the Rodeiro pensión Carpinteiras, and that was it. Did you have a different experience? There are no remote stretches, except for maybe the walk up to Monte Faro on a weekday, but you are always close to a road. I can think of no stretch of this route that takes you more than a km or two from “civilization.” The Invierno is ripe for “massification,” IMO because it is not strenuous or remote, has beautiful scenery, an increasing number of albergues, and can be done in stages under 25 km. You don’t need an ounce of “intrepidness” to walk the Invierno, just a good dose of self-reliance and love of walking alone. The forum guide is really all you need to have a successful Invierno walk.
But I have never heard anyone refer to the Olvidado with either of those descriptions. The marking is still rough in places. If you read a few of the older threads, you will get lots of examples of that. A few that come to mind — on the way out of Velilla del Río Carrión, into Buiza, out of Pola de Gordón, into Cistierna. IMO, a GPS is essential. There are marking efforts underway, but standardization and universal buy-in from all the governments, villages, and people along the way takes time. I think there is a trickle of peregrinos, but there are six or seven stages I would describe as remote, at least by camino standards. No villages, no people, no pilgrims, for kms. No vehicle access. It is true, though, that for a couple of those stages you can take an alternative on-the-road option. These are not technical mountain climbing stages, just some pretty hefty ascents and descents, but they are remote. I have never met another peregrino on the Olvidado. The closest I’ve gotten is to hear that someone is a day or two ahead of me. Some of the most spectacular scenery of any camino, to be sure, and I know you have lots of mountain experience, AG, but you shouldn’t think that you are likely to see others as you walk.
I love the Olvidado and I am not trying to discourage anyone from walking it, but I do think preparation and having your eyes open are important.
Buen camino, Laurie