I really enjoyed that. Going into it blind, it was very fun to watch. Not quite as good as Midnight, but then sequels rarely are. But I think it was a good choice to revisit it - if the humans have vanished, then the doctor wouldn't have been able to go to midnight and play a part in defeating the monster first time around, so it would still be there. The final ending scene was a bit cliched though, the episode would have been better to just end with the Tardis dematerialising.
The inclusion of a deaf character was done well, and the use of live subtitlers is a really great "future gadget" to invent and then explore in a sci-fi context, from how it can offer help, and how it can be used to exclude people easily.
The idea that civil servants that interact with the public must know a sign language makes sense to me - it might indicate that something about the Lombardy population has a high population of deaf people. Maybe a side effect of the war. That would also explain why they were all equipped with subtitlers available as a backup for everyone else. SLs are not universal though, so I guess the translation matrix can help "translate" gestures as appropriate to the local context just as it does text and speech (and BSL to us watching). A side effect of this is it would have been illegible to any American signers watching.
Exploring the wider plot about how humanity is gone makes me think we're facing a planet out of time situation, as we saw in season 4 (another callback?). Though if the lombardy are that similar to humans, they must be related in some way. I guess whatever that link is would have to come pre-2025, because we're not out in space yet, and we won't have any time to do so afterwards.
I really enjoyed this episode, this season is going very well.