Coinbase message Updated +Created
The input script of the Coinbase transaction can be anything, and this can be used as a Bitcoin inscription method.
Notable examples:
Daisy chain Bitcoin inscription Updated +Created
This is a term invented by Ciro Santilli, and refers to a loose set of uncommon Bitcoin inscription methods that involve inscribing one or a small number of payloads per Bitcoin transaction.
These methods are both inefficient and hard to detect and decode, partly because Bitcoin Core does not index spending transactions: bitcoin.stackexchange.com/questions/61794/bitcoin-rpc-how-to-find-the-transaction-that-spends-a-txo. This makes finding them all that more rewarding however.
On the other hand, they do have the advantage of not depending on any block size limits, as their individual transactions are very small.
Inscribing anything large would however take a very long time, as you'd have to wait until the previous payload chunk is confirmed before going to the next one. This alone makes the format impractical perhaps.