I really love the u8g2 library, but unfortunately I love my SSD1327 OLED even more. It supports 16-tone greyscale (which u8g2 cannot do) allowing 80s/90s video game style image dithering.

Getting up and running with lvgl was honestly kind of brutal, but now that it's done, I am generally happy with it. As you determined, it's much more of a UI toolkit than u8g2; the sort of thing designed with fancy thermostats and smart watches in mind. u8g2 has a menu toolkit but it is pretty narrow in scope.

I am planning on releasing a bare bones IDF-SDK v5.4 + lvgl 9.x + SSD1327 starter project soon so that I can hopefully save future travelers some pain.