Well I agree that it has its issues with selling it & earning a profit but due to the fact that this is a fighting genre the piece of the pie will never be as great as other genres that are more mast produced. The key to making UFE more profitable is to increase its potential mass awareness. I know that Capcom, Arcsystem works, Namco Bandi, Sega, & other publishers have in house engines of their own, but to increase the adaption rate we have to prove that UFE 2 source is worth abandoning be it Unreal, & their own in house engines. The only way to do so is to prove that this engine can be mainstream yet save them money & ease development @Mistermind. Now I'm going to outline a few ways this can be accomplished.
1) You need to develop a PDF for sale if need be that demonstrates & has as much detail on development as possible that covers cloning & creating staples of the fighting game genre, be it recreating street fighter 4-5, 2D fighters such as Street Fighter 2, Street fighter puzzle fighter, Blaz Blue, Skull Girls, MK 2, Marvel Vs Capcom 2, & now that you have full 3d movement Teken, Dead or Alive, Soul Caliber, & so on. Yes its great to add new updates but if there isn't a detailed way to learn to use the engine without asking for help as the first resort the features the more that are added become more of a hurtle for new & intermediate users, & only ensures that UFE 2 appeals to only established users & not towards gaining new users, which in the end decreases the adaption rate, if UFE 2 is seen as the easiest tool to make a fighting game it will be easier to sell it. As for the Manuel you can sell it on Amazon which will make it even more appealing as it would show up on a main stream store.
2) You need to create a detailed video tutorial series that will turn a beginner to a master of UFE for sale, you can sell it on Udemy, but I would advice selling it on Unity Learning platform to further establish that it is a key template to creating fighting games, it doesn't matter if its 5-24 hours long it needs to be made @Mistermind to have more exposure for the engine & easier understanding.
3) You can arrange that these tutorials as well as the future of the engine can be aided by supporting the patreon page.
4) We need to form that council I previously mentioned to vote & support a game being made with UFE 2, even if it is a fan made project, UFE needs far more mainstream appeal, & with the genre being as limited as it is we need to produce a game that can potentially attract the eyes of the public & publishers at large. Remember Virtual Fighter hasn't had a sequel in years, & other fighting games so there is a high chance that UFE might be the key to it. We need to support a game being developed that is going to sell within 6 months of release 100,000-250,000 units that can maintain 25,000 over 100,000 players a month online if its an original game, as for a fan made free to download game after 6 months it needs a download of 50,000-250,000 after six months of release with 10,000 over 50,000 players online a month.
5) A fan made game would be great for exposure, but to make profit @Mistermind we need to develop a game that is original & made from the UFE community council, with a 5%-10% royalty going to you @Mistermind the creator of UFE, & with my marketing knowledge it isn't really that hard to reach out to a youtuber & have them advertise the game before launching a fund raiser to fund it. UFE has a future its the best engine I know available to make a fighting game, & I understand that you are planing on getting it on unreal eventually though I would say support for Gedot Engine & Cry Engine should be first since they support C# then I would port it to unreal, because someone is already has a fighting engine on unreal no where near UFE but in time who know. If you can't prove that UFE is mainstream then there is no way it will have a high adaption rate I mean not even Blade Strangers was made with UFE, I don't mean any disrespect I'm just saying that we can either make UFE mainstream or wish its mainstream