When to take a probiotic - the label
As long as the manufacturer of the probiotic states the recommended time to consume them, first follow the indications written on the label.
When to take a probiotic - selected mushrooms
When such clues are lacking, a study by Canadian researchers (Tompkins TA, et al., 2011) provides us with some answers. In the results from this experiment, we can read that Saccharomyces boulardii mushrooms do not "pay much attention" to whether they are consumed on an empty stomach or during a meal.
When to take a probiotic - selected bacteria
However, the situation is different for bacteria of the Lactobacillus and Bifidobacterium species, more of which survive when given 30 minutes before a meal or on an empty stomach.
When to take a probiotic - general recommendations
Some of the more recent reports (e.g., Wastyk HC, et al., 2021), suggest that the human body will derive more health benefits when doses of probiotic products are administered frequently, throughout the day.