You're not the only one to mention that the 'HDR merge' option in Darkroom is one of the few real weak points. I still use
Mavic 2's and the 5D button on the remote alters the EV when it is flicked left or right, meaning that you can quickly increase the exposure value manually between each image by 1+ stop, super useful for HDR stacking.
Addendum
Another helpful hint - if you set the screen tap from autofocus to metering, tap the sky for shot #1, the horizon area for mid-ground shot #2 then tap the foreground landscape for shot #3 you'll get 3 exposures perfectly metered for each layer. Now try stacking them. Use the on-screen shutter button, not the one on the controller shoulder.
I tend to use different softwares for different solutions. With any form of stacking (exposure bracketing/focus stacking/averaging/super-resolution etc.) I'll import the images to CHASYS DRAW and run them through it's dedicated stacking module, let it do its stuff and then output to high bit TIF, which responds to editing and enhancement (Photoninja/Darktable) almost as well as a RAW does.