Posting solution here for other WSL 2 users. Since Julia is running inside essentially a Linux VM, the solution is to mount external and networks drive (i.e. /mnt/c, /mnt/d and also specify paths as linux paths.
So after mounting my SD card, everything worked
julia> @load "/mnt/d/wivaccine_rlow.jld" sols
1-element Array{Symbol,1}:
:sols