magento2 – Maximum of selected options in multiple select attribute in Magento?

We have a shop and have run into problem since multiple select attribute is set to “varchar” and can only have 255char. This means we can have aprox 51 different options per product but we need more that that.

We are using this selected attribute to layer navigation. We have tried to change from “varchar” to “text” and then admin is working but the layer navigation is gone. How can we solve this problem. We are using Magento 2.3.5