It seems impossible to find one single plug in for stock synchronisation for other major platforms.
I started running an online marketplace for small design brands, to save time for the designers from uploading and downloading csv, I have been searching for stock synchronisation apps for NON shopify websites for months with no result.
It seems to be a very basic request to me, or I am too naive ?
I hear your frustration! Trunk syncs inventory in real-time and right now it works with Squarespace already. We're currently already in the process of building an integration for Wix with their new API and there are plans for WooCommerce in the future.
Other than that, Trunk can also sync inventory between Amazon, eBay, Etsy, Faire, Shopify, and Square POS. Please let me know if I can help answer any questions/concerns!