I have a FO connection and I have noticed that if I switch the router off and on again to get a new IP it takes quite some time (almost 5 minutes).
If you access to the setting page of your router (from your web browser something like 192.168.x.x) you should be able to connect and disconnect your connection via menu.
In my case, doing so, changes IP in less than 10 seconds.
Had exactly the same issue as OP. Went from (ADSL, Ip changed within 10 seconds) to Fibre optic, changed within 30/60 minutes. The connection with Fibre Optics is more stable then ADSL so IP takes longer to change, also my line kept dropping daily, ISP stated it was at there end. I just reverted back, no issues since.
I have a UK FO which actually comes with two different frequency setting - 2.4ghz and 5ghz
If I just toggle between the two and refresh it gives me a new IP address
So are we saying that as long as you have a new IP address, that has never been associated with a limited or banned account, you are good to go? As in you wouldn't need a proxy or VPN?
In the US I had Verizon FiOS and I for the life of me couldn't get a new IP address. It was like hard coded into my router.
I even called them and they said they couldn't change it.