user14319: Do all transactions that are included in a valid block have to have at least one bitcoin address as part of their outputs (vout)?
I found this to be similar: Are Bitcoin transactions permitted to have no outputs (i.e. all inputs become transaction fee)? although not quite the same.

user21052: No.  A notable example of a pubkey script that doesn't typically include addresses or keys is the nulldata standard transaction type.  Examples of pubkey scripts that include public keys but not addresses are pay-to-pubkey (P2PK)[1] and "bare" multisig.
Although I'm not absolutely sure, I believe its allowed to have an empty pubkey script.  (That is, the compactSize uint that describes the size of the pubKey script is 0x00.)
Note: Bitcoin Core's getrawtransaction RPC, decodetransaction RPC, and other RPCs will display the public keys in P2PK, bare multisig, and redeem scripts as addresses---which can be a bit confusing.
[1] P2PK was formerly used for most coinbase transactions, but that usage has mostly disappeared on mainnet with pooled mining.  It's still a standard transaction type and quite common for coinbase transactions on testnet.

14319: <p>Do all transactions that are included in a valid block have to have at least one bitcoin address as part of their outputs (vout)?</p>

<p>I found this to be similar: <a href="https://bitcoin.stackexchange.com/questions/12451/are-bitcoin-transactions-permitted-to-have-no-outputs-i-e-all-inputs-become-tr">Are Bitcoin transactions permitted to have no outputs (i.e. all inputs become transaction fee)?</a> although not quite the same.</p>
 21052: <p>No.  A notable example of a pubkey script that doesn't typically include addresses or keys is the <a href="https://bitcoin.org/en/developer-guide#null-data" rel="nofollow">nulldata standard transaction type</a>.  Examples of pubkey scripts that include public keys but not addresses are <a href="https://bitcoin.org/en/developer-guide#null-data" rel="nofollow">pay-to-pubkey (P2PK)</a>[1] and <a href="https://bitcoin.org/en/developer-guide#null-data" rel="nofollow">"bare" multisig</a>.</p>

<p>Although I'm not absolutely sure, I believe its allowed to have an empty pubkey script.  (That is, the compactSize uint that describes the size of the pubKey script is 0x00.)</p>

<p>Note: Bitcoin Core's <code>getrawtransaction</code> RPC, <code>decodetransaction</code> RPC, and other RPCs will display the public keys in P2PK, bare multisig, and redeem scripts as addresses---which can be a bit confusing.</p>

<p>[1] P2PK was formerly used for most coinbase transactions, but that usage has mostly disappeared on mainnet with pooled mining.  It's still a standard transaction type and quite common for coinbase transactions on testnet.</p>
