[the_mitsuhiko]

That sounds like a somewhat pragmatic approach. Curious to see how that plays out in practice. I presume the total number of consumers that are interested in running their own ONT is limited. In Germany the situation seems a bit different. There customer owned Fritzbox devices with integrated ONTs are very widespread making the situation for an ISP quite different when it comes to upgrades.

[kuschku]

Sure, but even with the fritzbox situation all ISPs also offer dedicated ONTs as free rental or for 40€ as purchase. Some, e.g. Telekom, also offer SFP ONTs (Digitalisierungsbox Glasfasermodem)