Well. . . to begin. . .
The EX2 Ultra is a current device getting active support.
I have two of these things.
WD is in the process of upgrading the Operating System of these devices from “OS3” to “OS5”
The support forum under “OS3” has had a bunch of traffic over the last year or two. . .which has now dwindled with the release of “OS5”, which WD is pushing quite heavily.
The EX2 Ultra does support OS5. . .it was supported in the initial release of the software.
The OS5 forum has a “My Cloud EX series” subforum. . . . specific for the EX2 Ultra, EX2100 and the EX4100. The EX2, EX4 are not supported by OS5 (yet?). There are LOTS of posts in there.
Don’t get confused between the “My Cloud” and the “My Cloud EX Series”
As for compatibility. . .the device “dashboard” is accessed by a web browser. It works with MS Edge, and Chrome. I am sure it works on others as well. I “think” I have accessed from IOS safari in the past.
For “system compatibility” (to reach files) I can’t speak regarding anything MAC; but I do know you can readily reach it via WIN10 PC machines.
NOW. . . with the facts out of the way. . .let me give you some opinions;
The OS/3 operating system is old. Very old. WD has been very slow with feature updates and addressing system security vulnerabilities. I would not buy a new device with the intention of running OS/3. My existing OS/3 devices are fine. . .because they work for my purposes; and I try to keep them off the internet.
The OS/5 operating system is new. Very new. There are issues. Serious issues.
The web access capability (using WD apps/servers) has been lobotomized; and I find it now pretty much useless.
There is a HTTPS redirect function for the dashboard admin access. . .which seems to publish your system address with a DNS server. Many security minded folk abhore this feature.
Sleep functions don’t work. However. . .not sure it worked with OS/3 either.
Oh. . .the web access capability requires “indexing” of the “shares” that have web access. Think of a “Share” as a logical drive on the NAS. Typically, each user would be assigned a “Share”. The issue is that indexing is a horror show . Painfully slow (not minutes. . .it can take WEEKS); and it hamstrings the unit while doing it. FORTUNATELY, you don’t have to index a share unless you want to have WD App webaccess. . . . and since the apps are useless. . . . you don’t need to index. . . (Of course. . .the webaccess is the primary selling point of the NAS. . .)
I could go on a bit. . . .but you get the gist.
At this point, I have one NAS on OS/5; and two on OS/3. I ain’t upgrading the remaining OS/3 machines anytime soon.
I also am restricting internet access on the OS/5 machine (just like the OS/3 machines). . . .while I am pretty sure “security” of the device is better in regards to outside intruders. . . I am a bit leery regarding the OS/5 box phoning home a bit more than I would like.
Prior to 2021; WD was publishing new firmware every two weeks. Mostly minor bug fixes. In 2021, I have only seen one firmware release. . . I suspect the small bugs have been squashed. Leaving the fundamental design issues. . .which may never be fixed.
Note that for internet access, I rely on VPN. . .which is independent of WD servers. Works for me.
I also run Plex. . .the EX2 Ultra does have enough horsepower for this. . .but cannot do any form of on-the-fly transcoding.