Ask HN: Niche LinkedIn Platforms?

LinkedIn is clearly the largest amalgamation of different professionals on a single platform. Oftentimes, however, it falls short when you want to either connect with or learn about professionals in a particular niche (real estate, investing, content creation, etc.) Do you know of any LinkedIn-like platforms that cater to connecting niche groups? (Besides Discord/Telegram channels or subreddits). And are there any niche LinkedIn platforms you wish existed for your professional endeavor or hobby? If so, what would it be?