I agree about the acrylic blend, which will be elastic enough for him to get used to even stitches, and about cotton, which I find hard to work with.
Just not to confuse you/him, it’s actually Plymouth that makes Encore. Another nice blend I’ve used for a blanket is Berroco Vintage, which I found easy to work with and washes nicely.
Thanks mfolly1, I figured that mistake out after I posted and later reread it. Cascade has a good blend too, I just can’t remember its name off the top of my head. I love cotton and use it regularly for dish/wash/spa cloths but I’ve never thought it was good for brand new beginner knitters and I still don’t. Lack of flexibility, etc. Glad the new knitter in question is doing OK with it.
Whoooopsie - I completely missed that you said your partner is vegan, so I very much apologize for suggesting wool yarn and felting.