Did Starship make it to suborbit or did it RUD as well?
Seems like FTS triggered not long before planned SECO. Jonathan McDowell put it at -1740 x 150 km.
That vent that was there even before separation makes me wonder if there wasn't some shockwave damage during launch.
This one? That's ship engine chill, it gets redirected from the ship's engine bay down a pipe extending through the hot stage ring and is vented at the booster interstage level. It takes long enough that it starts before liftoff to be ready at stage separation.

Honestly exceeded my expectations, no scrub on a short window, sticking with 33 from the start and all the way up. Though I had also figured if the ship made it off, SECO would be a safe bet and its death would be during reentry, that was a tad disappointing. We have a clearer picture at the hot staging sequence, reducing to 3 at half thrust on the booster was known, but how many they relit for boostback and how many the ship ignited in one go wasn't certain. My armchair take would be maybe some pressurization issues during that flip for the boostback, only because it kinda reminded me of SN8 and SN9 not managing to relight. Pad seems relatively fine, having people back so soon is a good sign, there's a fresh dent on one of the tanks though, so something large enough still flew off. Aerial photos shouldn't take long.
Interesting to see what the next steps are. As the meme demands, B10 and S28 are/should be ready for engine testing and S28 at least is one step above 25, and if there's nothing new on the regulatory side for the ground systems or FTS, a January flight doesn't seem impossible. On the other hand, they were seemingly waiting on this one to install a new (horizontal) tank farm on the old landing pad area, and the existing tanks also have new pumps and subcoolers waiting to be piped in (to reduce prop loading to under an hour). But then this past week, pieces for a second tower started to arrive on site, so it might recontextualise that new tank farm they've been waiting on. IIRC there's room for some 9 horizontal tanks.