Li Shenron
Legend
I feel lonely being the only 'by the book' vote...
We're 2 now.
I am not sure what counts as "other official sources". We have Volo's but that's just extra creatures, not rules, so I think it doesn't count. I may or may not use Sage Advice.
Other than that, no evident rules modifications to the PHB, but it has to be noted that 5e has some areas where different interpretations of the RAW are possible. I may adopt a couple of interpretations which don't match the majority of gaming groups but they are still not rules modifications.
There are also "house rules" which establish social behaviour that the books don't cover (e.g. what to do with an absent player, or intra-party conflict) , but I don't think they are what the poll intends.
If you count these ones as well as interpretations of incomplete or conflicting book rules as "house rules", then it is technically impossible to play without house rules.