Speaking as someone who goes from bed to couch to bed during this pandemic due to a lack of desk space in my crampt apartment, I would murder someone if it meant I could claim their chair and desk and have actual lumbar support again.
Unless you had a recent surgery and the body is weakened or you have a serious condition (torn discs, etc) I’d advise to try to ditch all these crutches which end up weakening us up in the long term. However, I admit they could be very useful and help with back pain. I used to not be able to concentrate because of backpain and lumbar support did help at the time.
I tried sitting on a yoga ball for a while, but realized that it's not doing anything more for my back (because of how I already sit), but it's difficult to turn between my three laptops because the ball sticks to the floor and my clothes. So I went back to the chair. <shrug>
I do a fair bit of cycling and every-other-day core workouts that are kinda needed because cycling makes my hamstrings and lower back tight. It all happens to come together and I feel the same as you, much better shape in my 40s than my 20s.
I might dare to say I feel pretty darn good physically, most of the time. And can even push myself to pretty hard points (where things hurt, but not in an injury type of way) when I want. I hope I can keep this up, but sort of feel like a bunch of good practices that already are in place can lead to that.
[1] https://duckduckgo.com/?t=ffab&q=sit-up+pillow&iax=images&ia...
This probably wouldn't work out well nowadays with a desktop computer because desktop monitor sizes are usually way bigger than they were back then so you would have tilt your head too far, but it might still be fine with a laptop.