PSBT

BIP 174 defines a global map and maps for each input and output. They may carry UTXOs, scripts, key origins and partial signatures. [BIP 174 — PSBT]

A creator constructs the proposal, an updater adds data, a signer signs, a combiner merges compatible material, a finalizer builds the final scriptSig or witness, and an extractor produces the network transaction. One program can perform several roles; broadcasting is a further step. [Bitcoin Core — PSBT Howto]

A coordinator is not trustworthy merely because it supplies a valid PSBT. The signer must check the UTXO's link to the spent output, scripts and requested sighash; on a trusted display, the user checks recipients, amounts, fee and change against their own policy. [BIP 174 — PSBT]

Non-Witness UTXO carries the previous transaction, while Witness UTXO carries the relevant output; required data depends on the input type. Missing data must not be mistaken for a successful check. [BIP 174 — PSBT]

PSBT may expose balances, derivation paths or an xpub, and is not a key backup. [BIP 174 — PSBT]

PSBT v0 stores an unsigned transaction in a global field; an omitted version means zero. BIP 370 introduces v2 with separate construction fields and without that global field. [BIP 370 — PSBT Version 2]

BIP 371 adds Taproot fields to both v0 and v2, so Taproot support alone does not establish v2 support. [BIP 371 — Taproot Fields for PSBT]

Test the particular wallet, device and script combination through the whole workflow. Only once input conditions are satisfied can the transaction be finalized and extracted; node acceptance and block confirmation are separate events. [Bitcoin Core — PSBT Howto]