A lot of the pieces that entered Pink Floyd's "book" in 1967-69 were avant-garde space rock jams (though I'd say that only by 1969 did they start doing justice to them) - barebones set pieces that gave the band plenty of room to experiment with sound and noise in a non-melodic way. These guys might have been influenced by free jazz, but the links that were explicitly cited were to Stockhausen and to European free improv (specifically AMM).
I'm not a huge fan of watching movies of concerts, but I actually think LIVE AT POMPEII (from 1972), and the lengthy versions of "Set the Controls for the Heart of the Sun" and "A Saucerful of Secrets" - give you an interesting perspective on why they weren't just influenced by avant-garde music but by avant-garde performance art more generally.
Also, the guitarist is David Gilmour. The same guy who is known for tasteful, melodic, bluesy guitar solos on their megahit 1970s albums.
Yes!!! The UmmaGumma live album is a convenient, "widely distributed" way to sample this music, and is far from bad, but that if you want the *best* live Floyd from this era, that's not the place to go.
I like these versions fine, but they are both vastly inferior to the versions of this song the band was recording in 1969-70.