I wonder how reliable this is. Will AWS lightsail continue to work indefinitely for free? What if AWS changes the system in some way? What if the person hosting my locality becomes unavailable?

I suppose you can use any nameserver you like, the only problem is it’ll be a PITA to change it.

(I’ve recently registered a .bt domain by filling out a PDF form, hand-signing it, scanning and sending to a Bhutan Telecom admin. Changing a nameserver would probably be a similar procedure now, and involves a one-time fee if I recall correctly.)