Looks like FiiO launched the M15S in China. The volume knob is now dual mode which likely means Roon can control the volume if you disable the knob.
Some coverage:
[Edit: Added a reference to the hifigo.com sales page, which does mention Roon Ready]
It says Roon also here: āItās fully prepared for high-resolution audio streaming on Apple Music and is also Roon Readyā
The big Q: Is it a upgrade i SQ compared to F11Plus?
Torben
It looks like the current M17 will stay remain as FiiOās āflagshipā? However much of a ābrickā it is! 
Itās important to maintain muscle tone as we age. Consider your choice of the M17 an investment in your health and longevity! 
Do you have a current take on volume knob modes on the M17? For the short time that I had one, I used button mode to allow Roon to control the volume. I wondered if the M15S would go with a pure digital volume control but it looks like theyāve gone dual mode. The R7, for what itās worth, has a pure digital volume knob so no decisions or tradeoffs to make. You just use the knob and Roon can also control the volume.
Iām just curious what youāve landed on.
Hahaha!! It has to be. Itās a real ball-breaker 
Iāve settled on the volume wheel on the M17. I have Roon set the volume as fixed, and control the volume via the M17ās wheel. It works perfectly, as the FiiO is mostly to hand when Iām listening.
Although Iām also using its 4.4mm line-out balanced output to my Monoprice Monolith TXA AAA 887 occasionally. The Monoprice has a little more āoomphā to drive my Beyerdynamic T1ās (2nd generation) when Iām in the mood.
Thanks. The M17 is such a nice device. I suspect Iād like a physical volume knob - I didnāt like it initially on the M17 but I know more about how I use these devices than I did a few months ago.
The M15S is interesting - thereās a chance Iāll move to it and pass the M11 Pro on to one of my kids. My older one is 22 but is smart enough to still say āyesā to my hand me downs.
@gTunes - What benefits do you expect to gain compared to the M11 Plus? (If you donāt mind me asking)
Torben
Probably not much in the way of sound quality for my use case but I prefer physical volume knobs and Iād prefer the 4.4mm jack on the top. I also have a lousy habit of upgrading gadgets that donāt need to be upgraded.
Anyone taken the plunge here?
Iām very tempted. However much I just love my M17, the idea of a more pocketable Roon-ready solution appeals to me!
I slowly and carefully walked myself back from the ledge
Both the M17 and the M15S are designed to support the scenario in which an external power supply enables additional amplification modes. This is a very personal opinion but I donāt think either makes sense for me, given that I donāt care about that scenario and donāt need the additional electronics.
Following the M15S thread over on head-fi.org also had the effect of making me less interested. Thereās some reasonable criticism of the device in that thread. FiiO posted - on both their own forum and on head-fi - a series of articles explaining the M15S choices. Some of what they said was convincing but much of it seemed very defensive. The M15S does look like a great device but it sits in a strange place between the M11 Pro and the M17 - itās worth doing a deep read on the stuff Iām referencing before making a decision.
The head-fi thread:
The āR&D Storyā on FiiOās site:
https://forum.fiio.com/note/showNoteContent.do?id=202304101607138580488&tid=129
Iām sure youāll let us know what you do You canāt go wrong with any of these FiiO devices! Even if you decided to buy an M11S (the smallest unit) as a complement to your M17, that would make sense to me.
Thanks for the info. 
Iāve had a good read at the thread. It seems that most of the criticism aimed at the M15S is because of Android 10. I suppose I can understand that. Why launch a new DAP with an obsolete OS? But FiiO arenāt alone in this regard, and most new DAPās seem to have OSā a generation or two behind the latest.
Iām still tempted by the M15S, just as a more pocketable solution to use with IEMās out-and-about. But maybe the M11 PLUS would be a more sensible option?
In the meantime, Iām enjoying my KA-2 used with my iPhone.
Itās a really portable solution, and sounds great for the money with my balanced XBA-N3ās.
Ordered from FiiO-Shop and being delivered tomorrow (Germany). Looking forward to giving it a try. Will report back.
For clarification, if manufacturers want to customize Android, as is the case in most DAPs, the Android Kernel APK usage agreement hase some clauses in it that the current generation kernels (defined by Google/Alphabet) are not allowed to be modified and updates need to be enforced. This is to help protect the IP that is in the newest features of the latest Kernel, but also to ensure that developing patches and updates can remain consistent, without introducing some strange artifacts from developers that are not part of the core Android development team.
What gets taken out of the Android version is usually the cellular connection stuff built around the modem, but thatās also part of the core functionality within Android and what classifies it as the ācurrentā regulated version of the OS.
So, that is why you see these devices always on a few generations back. So, in conclusion, the āopen sourceā OS is only open source for older generations, not current.
Interesting context. Thanks.
HiByās new R6 Pro II is on Android 12. Somehow theyāre pulling that off.
I donāt personally have an issue with FiiO on Android 10. That may be because my phone and tablets are all Apple. Iām not irritated by the older Android experience because I donāt know any better.
Yes, you can pay to use newer versions, but most manufacturers want to use the less expensive or free versions. Also, you have to have a more talented software engineering team to make code changes, where as on the older versions there are more examples to utilize and jump off from, so you can do the work with less effort or less of a team.
Isnāt 13 the latest release though so essentially 12 is old.
Youāre correct. I did a lazy Google search before my previous post that showed 12 as the latest.
The HeadFi thread on the M15S is interesting - thereās back and forth between a FiiO guy and members of the community who push on the older Android version. The FiiO guy said something about their SoC provider only supporting Android 10. I doubt that he means Qualcomm. I suspect thereās some system integrator type company that does the core OS modifications and then offers them a hardware/software combo. This thread is actually clarifying why that intermediary might be stuck on 10.
There are new FiiO devices such as the successor to the M11 Pro due out this fall. Itāll be interesting to see if they move to something newer than 10. Not sure Iād care, though.
Adopting Android 10 is obviously a cost-saving move by FiiO.
But in the real world does it make a difference? I donāt know?
Unless youāre paranoid about security and have sensitive material on the DAP and connect to insecure networks all the time then itās all a mountain out of a mole hill. Create a non important gmail account without any card details.
Google/Alphabet is a company made to MAKE MONEY, not give away things for free. So, yes, ever version of Android that is not the current release can be considered OLD, but they still have core functionalities that are valuable, even if not the latest, and greatest version.
Iām not here trying to defend Google/Alphabetā¦ just trying to help people understand why the Android versions are where they are on different devices.