Apparently Skip Spence spent six months in a psychiatric hospital after attacking his Moby Grape bandmates with an axe. He wrote the tracks for Oar whilst there.
Other off kilter, out of sorts or just plain different artists from that era besides Syd Barrett, would be Wild Man Fischer, Sun Ra, The Residents, Captain Beefheart, Faust, Moondog, Throbbing Gristle, Holy Modal Rounders, Pere Ubu. Ya Ho Wa 13.
For me, Summerhill's LP from 1968 sounds very similar in approach to Euphoria. Daughters Of Albion I would need to listen to again. The Common People LP has similarities to Food, though it isn't as good in my opinion.
I don't think anything else really sounds like Puzzle and while Skip Spence is often compared to Syd Barrett, sonically they are not similar with one being very English and the other very American. Yes, they were both mentally breaking down and that can clearly be heard in both, but that is where the similarity ends in my opinion.
the amazing Syd Barrett's HYGIY? [have you got it yet] recordings. these have been collected and circulated by fans in numerous forms, but for the completist, HYGIY version 2.0 is the most comprehensive i've come across.