I used https://the-federation.info/'s Lemmy page to determine the current top 10 Lemmy instances as of the 8th of June 2023. The website only has sorting function for the current data, and the instances have to opt in to be included. Therefore, it is likely that some instances are not included. Furthermore, the website seems to only contain data from the last year, so the website do not have documentation on the top instances prior to this period.