Hi, I have coordinates of two points between which I am trying to calculate distance.

1 of the probable solution I found over the internet was to use Palladian extension, but it has become paid now. Can you please suggest any solution to calculate using open source free option?

Are you confident using APIs?
One solution can be making a series of API calls to an external service (Google, Here, Geoapify; something similar to this address Data Standardization - #5 by bruno29a, but with a routing service). How many distances do you have to compute?

Another solution is to compute a linear distance and increase it by a factor (10-12%) to simulate real distance. Not the most precise, but quick and costless. It might be an option.

It’s not too complicated, if you want I can create a small workflow, so you just have to insert your data and the api key.
Problem is that the number of calls is limited for free accounts (7000 for Geoapify per day, I guess).
That’s why I was asking the number of distances to compute. How many do you have?

If you are ok with the approximation, try to correct the factor. Take some addresses and calculate both real and linear distance; then calculate the average ratio between real and linear. You should get more precise results.