Highlights: Excellent location and a surprisingly well-equipped apartment. Extremely well-kept, clean and with easy access to the Copacabana beach and surroundings. There are plenty of local shops, bars, nightclubs and grocery stores nearby as well - which is a major plus.
Lowlights: The internet connection was overall very slow and unstable, so if you do WFH, bring your own hotspot. The shower was a major pain point, as it could not keep the temperature at a usable rate (it was either boiling hot or freezing cold - no in-between) and it took a lot of fiddling plus a technician's visit to be solved. Props to the host and his assistant in both regards, as they did their best to assist us.
The check-in process was a bit cumbersome, as the building's concierge was not very friendly (I should emphasize this is NOT the host's fault at all - it is entirely on the local administration but it didn't really cause any major impacts).
All things considered, I would certainly book again in the future.