Is it too late to add soil to this autoflower?

If you add more soil around the base it will start grow roots higher up, so its fine. Otherwise, you can just have a little fan near it making decent air movement and this will very quickly strengthen the stem. It's not a terrible thing to have a good space between the lowest branches and the top of the soil as it reduces the chance of bud rot, mould and fungus etc.

lo puoi fare in qualsiasi momento e su qualsiasi parte della pianta quello che ti consiglio è di non toccare il gambo e lascialo intatto perche le lesioni potrebbero far entrare qualche malattia indesiderata @BEACHBUDZ757 non è sbagliato ma il rischio c'è

You can definitely add more soil. Ive seen people actually lightly scrape the stem of the plant that you are covering with new soil to help it root faster. I’m not 100% if that helps at all but I’ve heard experienced growers do it.

No u can still @ soil .. more soil more roots 🙂