Install:

cd path/to/your/sublime/packages
git clone https://github.com/rsms/sublime-theme.git rsms-theme

You'll also need the fonts Inter and JetBrains Mono installed on your system, which are used by the UI theme.

Open the command prompt in Sublime (⇧⌘P), type "rsms:" and select an option.

• lights off — enable dark theme
• lights on — enable bright theme
• select theme... — quickly preview the themes
• toggle dark/light — toggle. Shortcut: ⌥⌘L

In your Packages/User/Preferences.sublime-settings:

"font_face": "JetBrains Mono",
"font_size": 14.0,
"font_options": [ "no_calt" ],
"line_padding_bottom": 1,
"line_padding_top": 0,
"highlight_line": false,
"show_tab_close_buttons": false,
"fold_buttons": false,

When in fullscreen, the square tab styles works much better than the default rounded ones:

"file_tab_style": "square",