My HV said my LG was ready at 4.5 months, but after her first two days of puree, she ended up very constipated and in pain so I stopped
Generally the advice is "around 6 months" when they hold their head steady and can sit comfortably upright in their highchair without slumping to the sides for the time length of the meal, when they can coordinate bringing food to their mouth and when they show an interest in food.
I think it’s generally 4-6 months old. We started with a little baby cereal in breast milk on a spoon and gradually made it thicker to build up to the purée consistency. Our girl was super interested in food so we began around 5 months as I was worried to start too early, she would sit next to us while we ate and would open her mouth for a bite, it was so cute!!
I agree with waiting until 6 months or at least very close, but to me the most obvious sign they are close is when they start trying to put your food in their mouth.
Your HV will be able to guide you on this