Ask HN: How to Get Beta Users?

We've built our MVP. We've kicked it around internally and with friends & family. It seems to work well though it is far from feature-complete. As of now we can probably support at most 100 users. Signup is easy and self-serve (auth with github; this is a dev tool).

We have an initial specific user profile -- individual developers who want to play around with AI/ML requiring GPU support but can't/don't want to futz with laptop GPU's but also cannot afford first-tier cloud GPU (starts at > $300/month).

How do we get beta users for this stage in our journey? How did you do it? We know the standard suggestions (hang out where potential users are; get on the radar of influencers; work on FOSS projects that our users care about...)

These are all great approaches, but frankly we are nerds and not well-versed in the art of social engineering. Any tips the HN community can provide would be greatly appreciated.