I have tried a lot of times to migrate the Multi-store website into Magento 2.3.4 and faced so many errors.
May I know the proper guide to migrate the Multi-Store Website into Magento 2.3.4?
I recently did a migration from 1.9.2.4 to 2.3.4 and importing the products, categories, customers and sales history was really simple using an external service. The store I migrated didn't have a huge inventory or a large number of customers and sales history.
I tried cart2cart and they turned out to be pretty expensive. Around $300 USD (they charge for the number of data items you're migrating), then I found Litextension and they only charged $59 USD. They offer multiple re migrations for 3 months afterwards as well. It might be worth trying as you can save a huge amount of time. If your products are organized by category pretty well then you should be able to import all your products and categories and then create the multi-store set up and assign the root categories to each store. It wont migrate all the backend settings and give you a perfect multistore right away but it will do the lions share of the migration work. According to "my understanding" you will have to set up all the configs for the multistore yourself.
I attempted doing the migration about 18 months ago without the help of these tools and messed around for ages with exporting/importing data and it was a bit of nightmare.
You can also do a demo migration with either service and see how it runs on your particular setup.