Google Maps says these are 2400 kilometeres, which could be done in 21 days of walking. I have some experience with Mathematics, enough to be wary that it would mean more than 100 kilometers a day. I wonder what's the mean walking speed Google takes into consideration.

I'd consider using the Eurovelo as much as possible.

Silent retreat dates:

Sep 27 2023 - Oct 08 2023 | Barcelona | Applications accepted starting Aug 27