SOLUTION: runs contrary to common knowledge, but what ultimately helped was:

• INCREASING print speed. The usual recommendation is the slower the better, but at that point, there’s no pressure control over the filament
• ENABLING retraction. Again, usual rec is to disable it for flexibles but turns out it alleviates too much backpressure which leads to filament buckling in the extruder

Also printing hotter than mfg recommends: I printed at 260 (10C over recommended maximum).

Thanks to u/Over_Pizza_2578 for pointing me to the right - opposite to everything else - direction.