It is possible that you can see devices on the ISP network. Normal the ISP device that you connect to (a modem for DSL and cable, or the ONT for optical fibre) provides this isolation/segregation. However some networks do allow you to see other devices on the ISP’s network if you don’t use a router to logically segregate your computer. There’s a couple of examples in this forum, e.g.:
This was probably the case for you too when you posted last year because installing a new router meant the other devices were no longer detected:
So if those devices have started be detected again then what has changed to allow this?