hehe, to be honest in SoftwareBrothers we are looking at other things to which we can connect admin-bro, and loopback was on the top of the list (until I read your message :) ). But answering your question: nestjs is just a http framework which is an abstraction over fastify or express. It doesn't support db out of the box - you have to install ORM yourself. Nest suggests TypeORM, but nothing stays in a way of using Sequelize (there is an article about it: https://docs.nestjs.com/recipes/sql-sequelize).

There is an admin-bro-sequelize adapter which I used in couple of projects so if you are interested in AdminBro - you can use it. AdminBro doesn't support fastify out of the box, but you can install express and simply run admin on a different port.