Plot 3d plane from x+y+z=6 equation in plotly

When x <- seq(from=-10, to=10, by=1); y<-seq(from=-10, to=10, by=1), x+y+z=6 is not plane but line.
You need to prepare more data points.

library(dplyr); library(tidyr); library(plotly)

x <- seq(from=-10, to=10, by=1)
y <- seq(from=-10, to=10, by=1)
z1 <- 6-x-y #For the first plane

origin <- tibble(x = x, y = y, z = z1)
# prepare all combination of x and y, and calculate z1
xyz1 <- tidyr::crossing(x, y) %>%
  mutate(z1 = 6-x-y)

plot_ly(x = ~x, y = ~y, z = ~z1, type = "mesh3d", data = xyz1) %>% 
  add_markers(~ x, ~y, ~z1, data = origin)

Orange points are the data you prepare (when x <- seq(from=-10, to=10, by=1); y<-seq(from=-10, to=10, by=1) , x+y+z=6 is line.)