Asklemmy

Bad posture can be the result of muscles holding onto dysfunctional tension. The problem might not be that muscle X is too weak, but that your body (really your motor sensory system) has developed the idea that holding tension in muscle Y is normal.

There are exercises or "movements" geared for this. Try looking up "somatics." It worked for me.

I don't know about posture but when I hurt my back a little while ago I found yoga and Pilates both very helpful.

Seated Rows, Bent Over Rows, deadlifts and squats

Tai chi, yoga, pilates are regular targets.

I do pulling exercises (back muscles), reverse crunches or leg raises (lower abs), and hip thrusts (glutes)! Also: stretches to open up the chest, neck stretches, lunges to stretch the front hips (hip flexors).

I try to do these every day or every other day. It doesn’t take much time. I’m not trying to build anything. It’s about good habits and maintaining strength in muscles that tend to weaken with prolonged sitting. All I really need is a resistance band - which has the added perk of being able to bring it on vacation:)

Farmer's carry.

Yoga: the Fish for instance.

I found soto zazen helpful here, learning how to sit still for several hours useful in getting to know basic body mechanics.

I still do rudimentary kung fu, tai chi, chi gung and aikdo bits I've picked up from good teachers over.

Swimming also useful as a full body, but low stress on joints, option.

The weather is grim here much of the year but even a few hours barefoot at the beach, park, garden helps get the feet working too.

Walking also a useful skill to work on.

Reverse planks, dead hangs and seated wall angels

Planks

Get a backpack that fits well.

Always carry a full liter of water in a heavy bottle in the bag.

It will remind you to keep your shoulders back and your abs tight.