Advice for a former writer starting anew

I want to return to writing a newsletter. About 8 years ago I wrote pretty regularly about a niche tech topic that I’m an expert in and grew an audience of 10k newsletter subscribers and 5k twitter followers. My day job starting consuming most of my time and I was burnt out from writing, but now I’d like to return with monthly long form essays about tech and AI.

The newsletter game has changed a lot I can tell. What advice do you have for someone who is a strong writer, deep expertise in a particular topic, and a decently sized professional network. Should I build on substack or ghost? Are LLMs going to make newsletters irrelevant? My goal with starting the newsletter over is to rebuild my professional brand with VCs, hedge funds, and tech execs as I’ve been heads down in my day job for the past few years. Thanks.