My favorite bikes are KHS Smoothie, Trek Pure, and Electra Townie step-through frames with BBSHD kits! ROCK ON IN COMFORT! ULTRA and MAX have ZERO parts support. BBSHD is nearly bulletproof and extremely popular with pedicabs.
I recently ordered an Allant+7 Lowstep for my wife. She’s been riding an analog Lowstep for years so it was what she wanted to stick with. I might have ordered a Stagger version but Trek doesn’t make one for the +7. Still this seems beefy enough to not have much frame flex.