Mine is 6m3w. I let him sit as long as he wants to. Set him up on the ground with soft surfaces around him so he can fall over to tummy time whenever he wants. I wouldn't leave him in a rigid sitting place (like a high chair or bumbo) more than 10 or 15mins. Otherwise should be fine.
Same, my lo can’t get herself into a sitting position. I sit her up and let her sit for a while until she unbalance and then fall back into tummy time position…I let her sit on high chair until she want to get out…
As long as wants if happy, that's the age they roughly can sit on own so wouldn't stop them
I just pop her up and put a pillow behind her - she’ll sit for ages until i pick her up or put her in a bouncer in the kitchen!
I just leave him there as long as he’s happy, he can’t get himself in to a sitting position but if I sit him up on the floor he will happily sit like that for a long while.