Do any other car seats apart from Nuna's fit the Nuna Triv Next stroller?

Hiya, Debbie,

In theory, they should. With these U-shaped adapters Nuna was making before (I am attaching a picture), you could add a Joie, Maxi-Cosi, Cybex, Recaro or Kiddy 0+ car seat. However, they are not available everywhere/always, so you have to actually find a Cybex Nuna Triv Next, or Maxi-Cosi Nuna Triv Next adaptor available around you or on eBay or something and get it. I am seeing a gradual decline of those availabe, so make sure to google and/or ask the Nuna distributor around you about availability - they may tell you more about the situation in your country and around – or get one from the already mentioned eBay.