Has an product attribute filter with checkboxes by default for category view ?
Multi select ajax filter are not magento default.
It would be available if your theme has given you the option for this. Otherwise you need to purchase plugin for this
This one is free, ajax based multiselect (Didn't tried it by myself): https://github.com/NikZh/magento2-multiple-layered-navigation
Mana Dev is free plugin, it allow you to select multiple filters at the same time. But it is not ajax based. https://www.manadev.com/layered-navigation-filters-multiple-select-magento-2
So if you need ajax based plugin then you need to purchase it. Following are some good ajax based multiselect plugins: