My favorite hosting solution for several years. It's lightweight, open-source and really stable. There are two general modes of operation: Buildpacks (e.g. Herokuish) and Dockerfiles.
On a freshly installed Linux machine, after installing Dokku you can push to Git repos on the server, and a container will be build and started for your app, with Nginx as a reverse proxy running in front of everything.
Installation
Linux
# download the installation script
wget -NP . https://dokku.com/bootstrap.sh
# run the installer
sudo DOKKU_TAG=v0.35.18 bash bootstrap.sh
Mac (Homebrew)
brew install dokku/repo/dokku
Plugins
General config settings
Change deploy branch
dokku git:set deploy-branch main
Timezone
dokku config:set TZ=Europe/Berlin
Nginx settings
Disable HSTS header
dokku nginx:set hsts false
dokku proxy:build-config
Max upload size
dokku nginx:set sitename client-max-body-size 25m
Ruby on Rails
Rails config
dokku config:set myrailsapp \
SECRET_KEY_BASE=mysecret RAILS_ENV=production \
RACK_ENV=production RAILS_LOG_TO_STDOUT=enabled \
RAILS_SERVE_STATIC_FILES=enabled