As per YIP-56: Buyback and Build Yearn is using the ecosystem fees to buyback YFI from the market instead of giving it to YFI stakers in ygov/yyfi vault. Governance staking and the vault should be yielding 0 APY currently.
The YFI vault, for now, is set to ygov and until it is updated, it will yield 0 APY. The YFI vault is currently not our top priority so I do not have an eta on when a new strategy will be made for it, if ever. Currently, it has a withdrawal fee but we are disabling it and it will be gone in a day or so.