So I have 100+ websites I manage for various clients, and it is a pain for me to login to their hosting or domain registrar accounts to manage their DNS.
Is there a simple solution, where I can turn on my own server that manages DNS? So for every domain I manage, I simply set a DNS once as ns1…com, and from thereon I can just manage their DNS configurations?
Yes. Bind DNS is the perfect candidate for that because it supports DNSSEC and everything in between. For DNS NS you need at least two static IPv4 addresses if you want to host it yourself.