There's an interesting "reverse job board" for Rails devs -> https://railsdevs.com/ that sounds pretty close to what you're looking for. I'm not sure what stack you work with but it might be of interest.
I don't know about rails but I've been part of Codementor (https://www.codementor.io/) for a while now and I found it works really well for small time contracting and building up relationships that can lead to bigger contracts.
Since I launched in November I’ve placed 10+ Rails developers with gigs. About half for full-time roles with salaries ranging from $100k to $200k.
For context, cold messages on LinkedIn have a 5-20% response rate. Usually on the lower end.
railsdevs is currently sitting at 50%+. If you’re hiring a Rails developer everyone is already half qualified - so matching is much more likely.