How can align the “Read More” buttons of all Blurb modules in a row when using multiple Blurbs with varying content heights?

To proceed, follow these steps:

In the row settings, set the columns to equal height.

Then, add the following CSS in the Divi Theme Options:

.et_pb_blurb_extended .image_card .et_pb_blurb_container {
    height: 100%;
    display: flex;
    align-content: space-around;
    justify-content: space-between;
    flex-direction: column;
}

.et_pb_blurb_extended.et_pb_text_align_center .et_pb_blurb_content {
    height: 100%;
}

.et_pb_blurb_extended .image_card {
    height: 100%;
}

.et_pb_blurb_extended {
    height: 100%;
    display: flex;
    flex-wrap: wrap;
}