A previous post by @markblundeberg here details a short list of possible differences wallets can form valid transactions. These differences allow for fingerprinting, a technique which can reveal which wallet software was used to create which transactions. This is a privacy issue which should be mitigated as much as possible.
BIP69 is a low hanging fruit on this list. The BIP69 full spec can be found here. BIP69 eliminates the ability to fingerprint a wallet via intput/output ordering for commonly used transaction formats by deterministically sorting the inputs and outputs lexicographically. BIP69 is not a part of consensus and is not intended to be.
As a step towards increasing the privacy of transactions, I encourage wallet developers to implement BIP69 and have it enabled by default (when applicable) in time for the may2022 upgrade. If you are not a developer please encourage the developers of the wallet you use to make this suggested change.
Below is a list of wallets who either already support or plan to support for May. Please make a comment in this thread if you have information about additional wallets that can be added to this list.
Wallets that use BIP69
- Electron Cash
Wallets that plan to implement it for May2022