Wanted to share this, I have a Dell Inspirion 2021, and couldn't get a dual boot, nor a full install of ubuntu LTA.
It was Win10 Bitlocker that was halting the process, you can google search the term bitlocker and ubuntu to look into correcting. But I'm just not that experienced and didn't want to learn. So I opted to load ubuntu temporary then open Gparted and deleted all partions, volumes, etc. Then powered down, inserted USB, tuened on, hit F12 repeatedly to force boot of USB, took me two tries with one shut off n back on to get ubuntu to load trial then it install to full install. Screw Win10.