I have the same situation almost. We have fiber from Telia delivered to the basement of our apartment building where it’s converted to cable by Tele2, who rents access to Telia’s fiber. Neither of them were willing to sell me or the organisation that owns the building access to fiber, even though it would have required only activating an outlet on whatever fiber switch thing they have in the basement.

Tele2 also has a monopoly on internet access; it’s that or 4G/5G.