Not sure if I have to disable anything else, but I disable the Matter app from the timeline a few days ago and the Aqara lock still gets logged every time is lock/unlocked.
The matter bridge shows as 0 device should I disable that one as well?
You cannot exclude the lock individually. If you want to turn off all security-related Timeline notifications (including those from the lock), you can turn off the “Timeline” toggle from “Security”.
If you still want to remove the lock from the timeline, you can use Homeyscript to delete these messages. You can schedule this script in a flow to run every hour or so.