Multi-Account Containers pretty much just enables a technology, FirstPartyIsolation, that's built into Firefox (and offers some UI for it).
The other extensions, which I know that use it (e.g. Facebook Container, Temporary Containers), aren't available for Android Firefox either, so I'm guessing, that technology just isn't implemented in Android Firefox.

So, yeah, you might have to go with a different solution:

• If you just need to sign into a different profile occasionally, you could do so in Private Browsing.
• You could install multiple different versions of Firefox, for example Firefox Beta or Fennec and then activate Sync between them.
• You could also make use of Android's Work Profile, which basically allows you to have the same app installed a second time, albeit the app in the Work Profile doesn't have access to all your files, contacts etc.. If you do want that, you can set that up with Insular, for example.