I have an old Mac mini in a closet that runs Ubuntu and serves as a Dokku [1] host. My side projects run for free and are accessible inside my network or if I'm on VPN. If the project gets enough love eventually it'll graduate to public hosting and the transition is easy because the app is already built with deployment in mind.

I have saved so much money over the years just not having to pay $20/mo * IDEA_QTY. The Mac mini doesn't take much power and is dead silent.

[1] https://dokku.com