Most off the shelf systems work with random pseudonyms: You generate a unique random number and store it only on the end user's system. Then you tag each data value with the random id one. These random identifiers do not count as PII so long as it is not possible to tie them to a real identity. So while you are of course required to follow data processing regulations, pseudonymous usage statistics with random identifiers is not against any regulation I know about at least. The lifespan of the pseudonym can be as long or short as you want e.g. last one session, one week, one version etc. But even when completely persistent, they will not constitute PII.