They almost show more active interest in each other when there’s a gate between them than with no gate?
That is pretty typical! Their behaviour can be completely different once the barrier is taken away. For better or worse..
Ignoring is not a bad thing, in my opinion. I think some time in closer space could work. A large space early on can be overwhelming or even distracting, for some rabbits during bonding. Ive seen this when Ive tried my older “single” rabbits together recently. In a small bathroom, they couldn’t avoid each other and actually sat close together much of the time. There was even some grooming at some point. In my larger, spare bedroom, they were both more interested in checking out the space individually. And when they came head to head during their explorations, they were reactive to each other.
It sounds as if the stroller could be a good tool for you when you start proper bonding. I think a bond could develop. It just takes lots of opportunities of them being together and learning each others ways. Letting that trust build.
Grooming is something that doesn’t always happen. Ive known of long term bonded rabbits that never do that. Many rabbits might want to be close to the other but that’s the only “affection” you’d see. It can change over time also. Ailis took to grooming Rumball more in his last year. <3
You can see it during bonding, and one may do it more then the other, but in the longer term, the roles reverse, or they just don’t groom each other so often.
The main aim is getting them to live together amicable and share resources.
You might see more territorial behaviours from Dax as Runa starts to mature. And some from her, of course. It sounds as if you are lucky on that front so far!