I find it strange that nobody has made adaptations for all this.
It is nothing strange, it is called intellectual property. In the Orbiter community, many addons like the mentioned Arrow freighter by DanSteph are subject to a closed-source license. As such, even if the binaries, meshes or textures could be altered to fit into the new Orbiter version, you would not be allowed to do so without explicit permission of the author.
Of course many of the authors are still active and promised to patch their work, but these are just promises until they deliver, and with some we are much over a year in the waiting already.
Now this would not be a big problem in itself if it were only for self-contained addons. Unfortunately, we especially see these things in middle-ware addons as well. Platforms like SC4, Multistage, OrbiterSound and UMmu all stalled due to the closed-source culture of Orbiter in the past and in the present. For some we've got alternatives (Multistage), for some we have not.
What also complicates matters is the
almost hostile attitude against one of the popular open-source licenses: GPL. IMO this severely hinders collaboration and effectively discourages developers.
However, it is what it is. Orbiter did well with it in the past and I'm pretty sure it will do well in the future. We might drop some jewels on the go, but I guess we have enough of them to afford it.
Just remember that it is free like in beer here, not like in speech. :tiphat: