chruby

For systemd services, this should be sufficient:

  [Service]
  User=slack
  Group=slack
  WorkingDirectory=/home/slack/porridge/daemon
  # sbin shouldn't be needed if you are running as a normal user
  # Environment="PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin"
  Environment="PATH=/bin:/usr/bin:/usr/local/bin"
  # I have had "chruby-exec[157986]: zsh:1: command not found: chruby" when using zsh
  Environment="SHELL=/bin/bash"
  ExecStart=chruby-exec 3.0.3 -- /home/slack/porridge/weather/bin/weatherd
  # This worked for some services but threw gem errors for others
  # ExecStart=/opt/rubies/ruby-3.0.3/bin/ruby /home/slack/porridge/weather/bin/weatherd

See instructions for cron, congifuring systemd environment and setting PATH for systemd.