I am not a very active writer, and so I have limited direct knowledge. But based on everything I see online and the emails I receive, it is hard to be enthusiastic about any e-publishers right now. Even those that were steady earners over may years seem to be going through rocky times and providing dwindling returns for the author's effort.
The erotic romance industry is maturing and the demands of the readership are changing. Back in the day (insert sound of nostalgic violin music here) the M/M readership (for examples) was growing rapidly and the authors supplying it could still be counted without running short of fingers and toes. It still felt a little like the fanfic frontier where readers where just happy to get something in the flavor they craved. But over time this readership has become more fragmented and more demanding.
Now erotic romance and adjacent subgenres cater to easily hundreds of discernable types and tropes of writing. The readership is very large, but also very well supplied by professional grade authors, many of them maintaining an impressive level of productivity. I went from being the new girl at the EPPIES watching (with some surprise) as grey-haired pros limped up to accept the awards inn he new erotica categories, to being someone who is increasing a semi-historical player in the industry -- watching to see where it will go next--knowing that I will probably not go there with it. (Released from my previous financial imperatives I am thinking of moving more into pure high fantasy ad just seeing how it goes--or maybe popular nonfiction).
I wonder how many erotic romance e-publishers are essentially in the same boat. To start a small press any time over the last 20 years you had to be a strong-minded person with a clear vision. But maybe that sometimes comes with a resistance to change? Some people were considerably less surprised about the closing of Amber Quill than I. They mentioned a tendency to keep publishing the same stuff, a bullish attitude to requested changes in their contract, and a general "my road or the high road" outlook. Kudos to AQ for see the writing on the wall and wrapping things up in a relatively tidy way, but maybe their drift from relevance offers clues as to what the e-publishers of the future will need to accomplish to survive and thrive.
I am not now, and have never been, a publishing professional. But from the authors side I see a future where publishers will have to actively locate underserved niches, recruit authors, and move their editorial interests constantly to keep profit in focus. And this does not mean just acquiring what editors think is hot (Steampunk FFS, it cool and everything but it will never be super-profitable) but some kind of empirical, analytical method for reading the evolving market.
I also see that there will always be super-hot authors who will bring in the lion's share of the profits. And as much as I, like most authors, resent back-alley favoritism, these authors will need to be given special consideration. After all, they have other options: going to another publisher or self-publishing for example. And the answer is not to lock them in with non-compete clauses and long term contracts, it is to sweeten the deal as an acknowledgement of the extra value they bring to a publisher and to the rest of the author stable under the same brand.
There is no particular publisher I would actively recommend right now, although there is always a long list I would actively discourage any new author from submitting to. When I finish my next erotic romance novella, I honestly have no idea where I will submit it, but I suspect it will be somewhere I have never submitted before--maybe even my first book self-published title that is not a reprint. My old strategies are not paying off the way they used to, and that means it is time to try new things. Even the old soldiers like Loose Id and Samhain look stagnant and shaky, respectively, and merit more of a wait-and-see attitude these days. They need to try new things too, and trying new things always brings with it risk of failure. But the earlier it is done the more resources they will have to plow through into pastures greener. Of the two Samhain shows more evidence of being willing to try new things, take risks, and make unpopular choices--but they also seem to be retrenching, so who knows.
If you still have an "I HEART Publisher" to share, please do. Be it a long-timer you still submit to and see steady returns, or a new kid on the block who is off to a roaring start. The erotic romance market, print and digital, is strong--and I am confident that as it develops and matures there will be recipes for success. But what remains to be seen is who, in the coming years, is going to discover them.