Just a quick post for Internet longevity. (There wasn't a dedicated Honda community I could find on Lemmy and fuck Reddit, so here I am.)
From what I could find online, some Honda and Acura owners will get stuck with a TT06 (or TT04) error when the system attempts to update itself. I bought my '23 Accord new and have been plagued with this for the last two years. This may affect other '23 models, but I cannot confirm this by just reading through rando Honda forums.
The first service bulletin with a fix, that doesn't work, is here for Accords: https://static.nhtsa.gov/odi/tsbs/2023/MC-10237040-0001.pdf The error will return after another update is available as it did for me. (Simply doing a TCU reset doesn't fix the issue.)
The Honda service tech will need to contact Honda and force an update override to get the latest TCU updates installed. (While I am not a Honda tech, I am a nerd. There was an off-by-one issue with time synchronization which I know can cause all kinds of issues with various flavors of hardware and software update systems.)
I had to call Honda and open a case with them directly, have them contact the service manager directly so they could get updated service instructions. (Weird.)
TCU updates that were installed for my Accord that seems to have fixed the issue: 
Cheers! I was just doing a brain-dump while this was still fresh in my mind and the firmware screenshots were still at the top of my photo list.
My apologies for a somewhat irrelevant post in this community, but cars.