Daily mobility work (even just 5 minutes in the evening makes a difference when done daily) combined with a hip hinge exercise a couple of times a week does indeed work wonders (it did for me).
As an alternative to the deadlift, I'd like to suggest the two-arm kettlebell swing. While there's no magic bullet in training, the kettlebell swing seems to come pretty close [1]. Plus, you can get one for home/work if you don't want to go to the gym.
I would however second the recommendation of learning exercise technique from a qualified trainer, particularly for hip hinge exercises - most adults, myself included, seem to suck surprisingly hard at what is one of the most fundamental human movements.
In case you do decide to go the YouTube route however, at least learn from a quality resource like StrongFirst [2], there's too many technique videos ranging from ineffective to plain dangerous.
Week 1 - 10 min stand, 50 min sit.
Week 2 - 20 min stand, 40 min sit.
Week 3 - etc...
Postural muscles take time to develop. Do the Agile 8 every day to work on your flexibility. https://www.t-nation.com/training/defranco-agile-8
The shortcut to an iron back is deadlifts, find a quality trainer and get in the gym for 30-45min 3x a week and you'll really improve.