The calculation of liquid junction potentials seems to be generally done using the Henderson equation. This is equation (8) in this paper. The paper also proposes a more accurate formula (eq 21-23), but probably we should be fine with Henderson equation. Then we need the activities of various ions (in fact "absolute mobility"). There's a Python library called PyEQL. We could use it or copy part of it.
The calculation of liquid junction potentials seems to be generally done using the Henderson equation. This is equation (8) in this paper. The paper also proposes a more accurate formula (eq 21-23), but probably we should be fine with Henderson equation. Then we need the activities of various ions (in fact "absolute mobility"). There's a Python library called PyEQL. We could use it or copy part of it.