@David-TP thank you for your response. The 'modem' is an Adtran 621 ONT provided by my ISP - Community Fibre (in London UK). Can't find any text that says if it has routing capabilities though. I...

Need some advice please. If I wanted to create 2 separate networks with a few Deco M5s, would that work? Or would they immediate recognise each other as a single mesh network? I think Option B won't...