So not really going to work in an open top aquarium then?
It can work, but!? It takes an awfull lot of time.. Eventualy they can addapt, tho maybe never will be 100% at their best. You need to transition a plant extremely slowly and controlled to make it used to less air humidity, especialy for a plant that developed submersed. A submersed formed leaf has a completely different cell structure than a emersed developed leaf. The submersed form misses the protective outer layer on the leaf making it evaporate all it's water withing hours and it will die. Plants grwon in nurseries at a 80 to 90% air humidity ar a tad more stronger, but suddenly reducing the air humidity over 50% resutls in the same story it will evaporate more water than it can take up and dry out.
It also might depend on the specific spp. how well they can adapt, some can other probably never will, it likely is an evolution thing. If it isn't evolved to grow that needed protective layer on the leaf it likely never will at least not in our lifetime.
SO first place it emersed in a controled 90% humidity invironment and very slowely and gradualy lower it over a periode of maybe 10% a month. Monitor it closely if you see a leaf suffer than it means you're to low or going to fast. This process can take up to 2 years or longer to make it be partialy happy. As said that might be all to it if you reach it's limit and than you have to be happy with a partialy happy emersed anubias..
I have one growing emersed that planted initialy submersed with only the leaf tips sticking out of the water. It took the plant 2 years to grow 4 leafs emersed and still they die pretty soon. I have no idea if this is the limit.. It maybe grows 1 leaf every 2 months, it lives happy a few weeks and than slowly starts to dry out from it's tip down. I have no idea how this will keep developing and how much longer it will take. It's a Anubuas barteri glabra, that has more size potential in proper conditions like this. This is about +/- 35% humidity.
Also have a small and very young Anubias barteri petite growing very close to the surface for a few months now. And because this plant is so small and grows in the filter outlet splash zone it has a much higher humidity. And thus much more happily growing emersed. But also here i guess i have to wait years to see how it finaly will turn out.
So yes it is absolutely possible, but don't expect miracles with gourgious growth very soon.
But if you have the patience, who knows..
I've seen a video whit a nice large Anubias frazeri growing emersed above an open top tank.. Also a multi year project..