The number of individual deaths really depends on the length of the campaign, but I went for “a few” over “a lot”. TPKs are pretty rare for me - I have had one, with a group of brand new players in the LMoP goblin cave.
It’s a potentiallu really brutal little dungeon, especially if the players don’t try to negotiate with the goblins. My players wiped the floor with the goblins in the ambush so they were feeling pretty confident and tried to take the ones in the cave head on and they just got buried by sheer action economy. But, I didn’t want their first D&D experience to end that way, so instead of having them all killed I decided the goblins would sell them to Neznar and we went straight into Out of the Abyss. Sadly, that adventure path is kind of terrible, so I kinda fast tracked them out of the Underdark and from there to Wave Ecco Cave so we would finish that campaign and move onto something else. Fortunately they all had fun and were excited to start a new one with a bit more experience under their belt.That is also the only TPK I’ve ever had - and it happened at the end of my very first session running 5e.