If you want an easy-blowing ergonomic Low D, I’d try the Dixon Low D, all plastic, with the conical bore (second from top in the photo below). Its combination of pleasant tone, easy air requirement, light weight, narrow tube, and smaller and closer fingerholes makes it a joy to hold and play.
Flutes and whistles with a conical bore, where the bore strongly constricts around the place of the lower hand, have the lower-hand fingerholes closer together while still being at a good acoustic position.
A cylindrical (parallel or straight) bore requires the lower-hand fingerholes to be splayed further apart, if they are to be in an acoustically acceptable position. Beware of cylindrical-bore Low Ds that claim to be ‘easy’ or ‘ergonomic’ : these usually have the fingerhole positions different than the standard positions that all the major good Low Ds use. There’s a reason all great-playing Low Ds are very similar: you can’t defy the laws of acoustics!
Here you can see the Dixon and six different cylindrical Low Ds, and note how similar the fingerhole positions of the six are
1 old Susato keyless with angled neck
2 Dixon all-plastic two-piece conical bore
3 Reyburn with maple head
4 Reyburn with poly head
5 Burke Pro Viper alloy
6 Kerry Optima
7 MK tunable (like the MK pro but made before that designation was used)

You’ll note that all have Hole 6 smaller than Hole 5. Were Hole 6 to be acoustically ideal it would be the same size as Hole 5 and placed more or less exactly between Hole 5 and the bottom end. (It’s where that hole is on a Boehm flute.) Trouble is, nobody could reach the hole if it were way down there! So all the makers compromise (between the laws of acoustics and the human hand) by moving the hole rather further up than it should be, which makes the note too sharp, so the hole size has to be reduced to compensate. This results in a Low E on most Low D whistles which is weaker than its neighbors. Whistles I’ve tried which were called “easy” or “ergonomic” had Hole 6 even further up, even smaller, even weaker. You can’t fool Mother Nature!
The surprising thing to me is what an enormous difference in hand comfort is created by a rather slight difference in the hole spacing of the upper hand. In the photo above all the Low Ds, with one exception, are comfortable for me to play. The maple head Reyburn, with its upperhand holes only slightly larger and more widely splayed, is difficult for me to play. I wonder why the maple head Reyburn has the upperhand holes further apart than most Low Ds including another Reyburn.