Feeding nutrient free soil

How often should you feed a plant that's in soil that has no nutrients in it ? If I'm liquid feeding a soil that hasn't been amended with anything. Is it like coco at this point or does it store nutrients from every time you feed ?

Frequently and with micronutrients supplements in ratios that benefit the plant.
And get more microbes in there- compost and or worm casts top dress, AACT or extract.
You will build up some nutrients in the soil. But correct ratios and amounts of course. Some have stronger affinity to stick around and on excess exclude other minerals. Also pH from salt build up is not uncommon.
Get some dolomite lime to use this year. Its cheap, goes a long way. Calcium and magnesium. As well as buffers the pH up towards 7.0.

If it's in soil without any nutes isn't considered soiless

Parsing words and terms....oh the passive agressive too many redbull or monster response

If it's bagged and made its not soil. Just a medium. Sure. Now we're all media growers?

If it's bagged and made and has ZERO nutes must be Tupur.