Years and years ago, I had a pair of combat boots that had been modified with an integral holster. I carried a Walther PPK/S with no problem, except of course for bending over, hiking up my BDUs or jeans, undoing the snap and finally drawing.
These days, I wear cowboy boots and have never found a solution that allows for COMFORTABLE ankle carry. Standard ankle holsters just plain don't work under cowboy boots. The few that supposedly clip on or otherwise attach to your cowboy boots didn't work well for me either. Besides, I don't have the need to carry a backup weapon anymore. (But I did buy a Bugbite concealment holster last year. Gave it to my (adult) kid after wearing it around the house for an hour.)