Thanks, folks. This fixed my issue. Both of the following options worked for me, but I decided to go with captions always on in the end. Here's the code I used in Brine:
//change dot to open captions on mobile//
.sqs-lightbox-meta-trigger {
padding-top: 25% !important;
padding-left: 90% !important;
color: #C1D32F !important;
font-size: 1em !important;
font-family: 'BikoBold'!important;
margin-right:50px;
margin-bottom:50px;}
a.sqs-lightbox-meta-trigger:before {
content: "Click here";
visibility: visible;}
You could change the colour of the text, font size, font, etc. I also added in margins to move the text a bit up and over from the bottom corner. Obviously, someone could also change Click here to whatever they wanted.
In the end I went with code from above that just made the captions come up always: //Show gallery captions all the time on mobile//
.sqs-lightbox-meta.overlay-description-visible {
bottom: 0px !important;
}