Alright, I did a fix.
Rather than trying to output the low var in my template, I decided to first stash it the same way I stash my other listings.
So I did this first, in my page type:
{exp:low_variables:pair var="var_eleads_countries"}
{stash:code}{var_eleads_countries:code}{/stash:code}
{/exp:low_variables:pair}
{/exp:stash:set_list}```
And then returned it like this in my stash_template:
```{exp:stash:get_list name="countries_listing"}
<option value="{code}">{code}</option>
{/exp:stash:get_list}```