I would need an alternate asana
It most likely has to do with my lower back. Ive had a stiff lower back for quite some time, I couldnt even sit up on a 90 degree angle with legs stretched straight in front of me when I just started yoga.
I can now though.Its like trying to jump without being able to finish the whole motion.
Ive done headstand in the past but, Ive had some spinal issues, places that hurt so I got it checked and the results were to the point that it just wouldnt be safe for me to do a headstand or tripod.
I think in regards to that, the "suggestion" to master tripod and headstand, though well meant, are ill fitting.
There are also other exercises that will strengthen the muscles needed, and other prep work or work that would help you achieve a strong, straight, non-banana like handstand.
They're usually found if you look at calisthenics, and one of the exercises mentioned is the "hollow body". Which seems to also be needed for effective pullups.I also have lower back flexibility issues, but I'm actively working on it. In past I could not also sit up on the floor in 90 degree angle without strong effort. Have you tried head to knee pose? It is very effective for lower back. https://www.yogapedia.com/yoga-poses/head-to-knee-pose-a/11/11229
That hollow body seems like pretty good core workout. Many KY kriyas work on core as well.

