You may try a JS customization ( as described below ) to remove + sign from custom option price dropdown.
I assume you are using a custom theme, let your custom theme name is "Vendor_mytheme".
Please make sure you are on Developer Mode.
step 1) Create requirejs-config.js file under /app/design/frontend/Vendor/mytheme/Magento_Catalog/
File : requirejs-config.js
var config = {
config: {
mixins: {
'Magento_Catalog/js/price-options': {'Magento_Catalog/js/price-options-mixin': true},
},
}
};
step 2) create the js file price-options-mixin.js under /app/design/frontend/Vendor/mytheme/Magento_Catalog/web/js/
File : price-options-mixin.js
define(['jquery'], function ($) {
return function (widget) {
'use strict';
var globalOptions = {
optionTemplate: '<%= data.label %>' +
'<% if (data.finalPrice.value > 0) { %>' +
' <%- data.finalPrice.formatted %>' +
'<% } else if (data.finalPrice.value < 0) { %>' +
' <%- data.finalPrice.formatted %>' +
'<% } %>',
};
$.widget('mage.priceOptions', widget, {
options: globalOptions
});
return $.mage.priceOptions;
}
});
step 3) Remove static content and cache using below commands from your Magento root directory
sudo rm -rf pub/static/frontend/*
sudo rm -rf var/view_preprocessed/*
sudo rm -rf var/pub/static/*
sudo rm -rf var/cache/*
sudo rm -rf var/generated
sudo rm -rf var/composer_home
sudo rm -rf var/page_cache
sudo rm -rf var/view_preprocessed