Prior to 0.19.0, creating outputs with an unknown witness version was considered non-standard. This was a violation of BIP 173 and was fixed for 0.19.0+ in PR #15846.

On 11/16/2021 10:17 PM, n1ms0s via bitcoin-dev wrote:

> Hello all,
> I am currently working on a fork of bitcoinj with basic Taproot support. Currently it supports basic sending and receiving with Taproot addresses using a bitcoinj SPV wallet.
> See here: https://github.com/n1ms0s/bitcoinj
>
> It supports the above along with public/private key tweaking. Feel free to take a look, and leave feedback or even work on it yourself and submit a pull request.
>
> One issue I am running into right now though is when broadcasting a Taproot transaction to older nodes (old as in ~0.18.0) I get an error response of "Witness version reserved for soft-fork upgrades". Anyone have any idea why this happens? I have a stackexchange question open here for it:
> https://bitcoin.stackexchange.com/questions/110787/issue-when-broadcasting-taproot-transaction-to-older-nodes
>
> n1ms0s