Inspired by a Reddit post, here's a mix of ambient, beatless tracks from across a number of Autechre albums,

lux 106 mod - PLUS 
iris was a pupil - Move Of Ten EP 
ylm0 - Move Of Ten EP 
notwotwo - Quaristice.Quadrange.ep.ae 
wetgelis casual interval - NTS Sessions 1-4 
Yulquen - Amber 
Altibzz - Quaristice 
paralel Suns - Quaristice 
esc desc - SIGN 
r cazt - SIGN 
32a_reflected - NTS Sessions 1-4 
carefree counter dronal - NTS Sessions 1-4 
oneum - elseq 1-5 
Perlence Suns - Quaristice.Quadrange.ep.ae 
Altichyre - Quaristice (Versions) 
gr4 - SIGN 
shimripl air - NTS Sessions 1-4 
Metaz form8 - SIGN 
see on see - Oversteps 
pt2ph8 - Oversteps 
sinistrailAB air - NTS Sessions 1-4 
acid mwan idle - NTS Sessions 1-4 
VI Scose Poise - Confield 
peal MA - NTS Sessions 1-4 
eastre - elseq 1-5 
mirrage - NTS Sessions 1-4 
ii.pre esc - PLUS