I would pay for it.
Having said that, yes, the current version needs to be fixed up a bit. That is clearly what the developers would want to do, that is why the current version is Beta, etc.
But there are other things to consider. Many regular Linux desktop users work hard to never pay for anything. There is probably little overlap between the community of writers and Linux users. If everybody who is active and interested in Scrivener for Linux on this list bought a copy, would that fund it? Not sure.
If I was the developer, I would consider coming out with a functioning (bug-free-ish, fixed up install to allow in line spelling without extra work,etc.) version of Scrivener for Linux and include the licence for that with the paid lic. of any other version. A Linux-only version could, for a while, be lower cost or free. Then, run it that way for a while.
Once there is a post-Beta version of this software for Linux, available in any way (free, paid) it would get a lot of publicity. It would be a big deal in the Linux community. I would personally get involved in helping that happen.
For now I think there is a second thing we (Linux users) should consider.
In addition to what you might pay (or not pay), what features would you do without? Scrivener has a LOT of features, some of which are essentially redundant in basic function though diverse in implementation. For example, you can put notes on a project on a car, in a project note file, in a scene note file, and things that might be in notes can also be in various kinds of pre defined or user defined meta data.
I wonder if there is a subset of features that this community could say, “don’t bother with the first non Beta release, we can live without it for now” that would make the developers produce a sigh of relief and encourage them to move forward.
A similar approach might be to ask the developers. What five or six (or more) features would you like to remove from SfL for now in order to make it possible to move forward with an official release that simply lacked those functions, with the promise that future versions would have that?
Also, should SfL have special Linux features? For example, the default should, perhaps, be to treat scenes as files and have that be normal, so Linux users can edit specific scenes, without any trouble at all, using their favorite editor (emacs, gedit, vi, etc.). That would make Scrivener very Linuxy (culturally) and would attract more users.
Here is the market, perhaps: People who got a Mac, love their Mac, but eventually came to the point where they can’t keep using a Mac because, say, the latest version of the OS requires that they buy a totally new computer (as happened a few years ago). The Apple ecosystem requires the kind of investment that makes it ideal for people with real jobs or industry support.Scrivener is ideal software for writers. Therefore there should be a small but steady flow of Mac users switching to Linux. That, to me, is what SfL is for. A small but important market.