(How) can I get a Moto G4 plus upgraded to Android 8 Oreo?

I have a Moto G4 plus which is still on Android 7 Nougat whereas I expected it to get updated one more time, to 8 Oreo. This has become a problem because some apps have now stopped working on Android 7. I guess the main question is whether the phone is eligible for Android 8 in the first place, but I found this thread which seems to confirm that it is: https://forums.lenovo.com/t5/Moto-G4-Moto-G4-Plus-Moto-G4-Play/Android-8-update-not-received-for-Moto-G4-Plus/m-p/5031326 I note that the above forum post has a link to “LMSA” which now redirects to “Rescue and Smart Assistant Tool”. Is it possible to estimate how likely it is to work? It could take a lot of effort itself, as I don't currently have access to a windows computer (I do have windows on a dual boot laptop but the windows has recently stopped working, long story). I have a vague recollection that major release updates are prompted by carriers/operators, is this where my problem is? I bought the phone from Amazon UK, the listing headline was “Motorola Moto G4 Plus 16GB SIM-Free Smartphone (Dual SIM) - White (Exclusive to Amazon)”. Could it be that the version exclusive to Amazon doesn't get Android 8? I use it with two Sims, one on o2 (UK), one on Orange Poland. I had a look at the the settings to see what info might be relevant. The software channel is retgb and the version in hardware info is PVTB. Please let me know if any other info is needed and I'll edit it in.