Who do you talk to when you have architectural questions? Where do you get feedback on design options? When you want to discuss tradeoffs of those options who do you talk that over with?
I am one of two technical cofounders for a small software company. We have really good discussions about the design of our product. I am pretty good at searching. We are comfortable weighing alternatives and making a decision and living with the consequences. All that said, sometimes I want to discuss with other people some of the design challenges we face, or seek input on how people have approached the problem.
Are there fora that you enjoy for such discussion? It seems that it does not fit with the theme of most Q&A sites. Most IRC channels I know of are pretty focused on their own specific topic.
2. Make a blog post and share on HN
3. Let the commenters tell you everything you did wrong and what they would have done instead
Put more seriously—I think if you don't have an external professional network to lean on, then you should blog it, talk at conferences, etc. Saying "we aren't sure this is right but it's what we came up with" will definitely invite comment. Keep an open mind and remember any publicity is good publicity: your harshest critics will still be engaging and giving you feedback.
I don't think chat services (IRC, Matrix, Discord) are a good fit here, unless used to talk to a group of people you already know and have some cachet with. But I might just be old-school.