Babies guts do not magically mature ready for solid food the night they turn 6 months....
That is just a guideline as the majority of babies are ready then. Many are ready earlier.
Never start before 4 months. There are then 3 things to look for:
1. Baby can support themselves well enough to eat, I.e their head isn't flopping down all the time and they can sit in a high chair (they don't have to be sitting completely unaided)
2. Baby has the coordination to pick up finger food and put it in their mouth themselves
3. Baby wants to do it and doesn't push the food out again with their tongue, which is a reflex they lose when their gut matures.
Luckily when baby meets the above criteria it means they are ready, if they do not you need to wait. Don't give wheat based food before 6 months. Don't give honey or cows milk as a drink before 1 year.
I appreciate guidelines are important but I like to read into why they have been set as they are often a 1 size fits all, including third world countries and slow developers. We started giving Scarlett bits of finger food to play with and chew at 4.5 months, she didn't 'need' it but she really enjoyed it, and we discussed it with our HV first to make sure we avoided anything that could be harmful.