Maybe it'd help to modify a window manager, to very slowly change the position of things on screen. This would be especially effective with a tiling WM in dark mode, so there aren't any large areas of lit pixels.

There'd be some details to work out, like making sure you don't trigger word wrap changes. One approach would be to leave a little border on at least one of the screen, so you can move everything together horizontally without changing window widths. In the vertical direction maybe you can get away with changing relative window sizes slightly.

(On the other hand, if you're mainly using text in dark mode, maybe your fancy OLED screen isn't benefiting you much.)