I finally rigged the octopus in Blender and rendered a quick test in Eevee. Still a long way to go before realistic movements, but the rig is capable of them so I hope to show one soon!
Edit: I added a second video, 1,33 seconds long, that will be the start of a serious animation of it moving around, swimming and breathing. This 40 frame video took me 4 hours to make, 5 minutes to render with Eevee in Blender.