Since at least the start of 1.16 after you beat the ender dragon a second time you can obtain a second dragon egg. I have tested this in a world with and without cheats, happened in both of them. If you want to test this beat the ender dragon take the egg and then re summon it and beat again if you do not see a second dragon egg leave end and come back.

sorry I don't have an gameplay of this but I do have two dragon eggs in a world with achievements