The WordPress theme Silverbird from WP3Layouts is in my opinion a nice, simple and rather clean theme. It was first released in 2018 and saw a few updates in the next few months. After that it dried up.
There is also a Pro version for sale, but I don’t really need features in a theme, that is what plugins are for.

I do use the theme myself, but saw that it didn’t work in WordPress 5.6 anymore, due to jQuery updates. It does work with PHP 8, which is quite nice.
I don’t expect any updates coming from the original author.
I forked the theme as Silverbird Lite, which is now available on Codeberg. I don’t intend to do much with it, just keep it in working state. I did remove a few things, like Google Fonts, since I don’t like my visitors being tracked by Google.

The first changelog looks like this:

• = 1.1.0 =
• 2020-12-10
• Rename to Silverbird Lite.
• Tested on WP 5.6 and PHP 8.
• Fix preloader and disable it by default.
• Update Bootstrap.js from 3.3.6 to 3.4.1.
• Remove old modernizr 2.6.2.
• Remove Support tab in Customizer.
• Remove Google Fonts, there are plugins for that.
• Remove Google Plus from social media links.
• Remove Swipebox, you might prefer your own image modal.