I tried using "signif()" function as well, but was having issues. The reason this is important, is because R rounds up the y-intercept value in the equation. In this case it's 11: y = -0.013x +11. However, it should be 10.81 (according to excel). Is there a way to get around this, so it doesn't round up?

I think that unfortunately ggpubr has not been designed to let you tailor this in a super elegant way, though perhaps you could request that from the ggpubr creators as a feature request.

You can however completely control what is printed, but you may need to do additional work, to cobble together the elements you want. Here is an example. First I show the out of the box rounding that ggpubr naturally gives you. thereafter I demonstrate arbitrary precision (i chose 3 decimal points, but you can do anything here).

library(tidyverse)
library(ggpubr)
#out of the box
ggscatter(mtcars, x = "wt", y = "mpg", add = "reg.line") +
stat_cor(label.x = 3, label.y = 34) +
stat_regline_equation(label.x = 3, label.y = 32)
# construct your own formatting
(mylm <- lm(data=mtcars,
formula=mpg~wt))
(my_eq <- scales::comma(mylm$coefficients,accuracy = 0.001))
(my_eq_text <- paste0("y = ", my_eq[[1]], " ",my_eq[[2]],"x"))
ggscatter(mtcars, x = "wt", y = "mpg", add = "reg.line") +
stat_cor(label.x = 3, label.y = 34) +
stat_regline_equation(label.x = 3, label.y = 32,
mapping=aes(label=my_eq_text),
output.type="text")