Following is a response from Senior DHS staff member, Ali Roghani:
The warning you are encountering when using tbl_svysummary() from the gtsummary package is likely related to how the weights are scaled in your survey design. In R, the svymean.survey.design2() function is quite strict about weight scaling. To eliminate the warning, you can inflate the weights column so that it sums to the number of individuals it actually represents, rather than the number of survey respondents. Here's how we can do that:
# Adjust weights to sum to the actual population size
total_population <- 25000000 # Replace with your actual population size
mydata$wt_scaled <- mydata$wt * total_population / sum(mydata$wt)
svy_design <- svydesign(id = ~hv021, data = mydata, strata = ~hv023, weights = ~wt_scaled, nest = TRUE)
Using the adjusted weights in your svydesign() may eliminate the warning.