You are being obscure.
You can get ADSL, (or ADSL2+ ?) from what you said earlier. Anyone who can do that can also get the "VOIP" service. So the loss of PSTN makes no difference to them.
The question of getting decent broadband speeds is completely unrelated to PSTN.
In your particular case the 10Mbps USO requirement kicks in, but if like myself you are using mobile broadband at above 10Mbps that doesn't apply to you. I assume you have checked out whether or not Openreach currently intend to supply FTTP to your area.
I just realised, re your Subject
, you start from the wrong place. Copper is not being retired, and won't be for a long time.
My broadband basic info/help site - www.robertos.me.uk.
Domains, sites and mail hosting - Tsohost
Connections: OnePlus 8 Pro max 165Mbps down, 24Mbps up on Three, and B311 4G, tbb tests normally 35-45Mpbs down, 65Mbps off-peak, 9-24 up.
The EU’s multiple failures are due to a deeper malaise .... What malaise? The EU’s formidable immunity to the smallest amount of democracy. New Statesman Feb 2021.