My son has been laughing for a month or so.
My baby is 6 months and she is not easily amused I’ve had her laugh a handful of times but I have to be doing something really funny otherwise she’s unbothered.
My baby has been laughing for many months now but my friends son is 8 months and she said he’s only laughed once
Some days my little guy is just moody and serious and some days he’s easy to make giggle. He could just be in a phase. Mine didn’t start giggle more and bordering on being a full out laugh till recently. Maybe the last two or so weeks. It couldn’t hurt to bring up and see what the doctor says! But I feel like you’re fine and on track!
My 5 month old is laughing, but like you said, all babies develop differently. You can mention it but if that's the only milestone he hasn't hit yet then I doubt they'll be very concerned.