If you fix a pull-up bar in a doorway you’ll just end up banging your feet/knees on the floor all the time because of the low height it needs to be fixed at so that you don’t bash your brains out on the top of the door frame 😀
I live in a terrace in which the bottom 2/3rd’s of the stairs are between two walls, so I’ve fixed my pull-up bar above the bottom of the staircase.
This way, it’s at a good height so that I’m not catching my feet/legs on anything, and there’s nothing above to worry about banging my head on.
Can’t remember where I got my pull-up bar from though. Might have been Argos. It fixes to the wall using screws, and has coped with my 13-14 stone weight for several years without failing … 😕 (there, that’s cursed it now)