My LG turned 9 months last week, she always liked to sit up and play but we had to put her in the sitting up position as she couldn’t do it by herself. Only two days ago she started to sit up by herself. She also rolls both ways and doesn’t mind tummy time but doesn’t crawl yet. She pivots a lot and goes backwards. I wouldn’t worry.
My little boy (9 months last week) is exactly the same. Happily sits for ages but can't get himself to sitting, hates being on tummy so just rolls onto back, loves being on his feet so pulls himself up on me, shows absolutely no interest in crawling/army crawling/bum shuffling. He has just started pivoting in a circle on his tummy but this is usually so he can get his hands to me to pull him to standing. I'm not worried. He is making progress very slowly and he's hitting other milestones so he'll get there eventually.
My boy will be 10 months next week and he’s only rolling and sitting, though he can’t get himself into a sitting position. He doesn’t to pull himself up and he’s not showing any interest in crawling either, I’m not worried about it right now because it can happen as late as 18 months for some! X
I know a few that walked before they crawled. And many many babies aren't crawling yet at 9 months so no worries. Do you have a health visitor to get a 9-12 months assessment? That should put your mind at ease because it's by 12 months that these things are expected, not by 9 months. Even some aren't crawling by 1 just different with all babies xx