A great website I’ve been using is
https://blockgametracker.gg/
It gives a lot of information and extra graphs about the average playercount over the past days, peaks, means…
Simply select which server of which Minecraft edition you wish to view playercount data about at the top of the website and you’re good to go. The data goes all the way back to 2017 for CubeCraft Java and back to end of 2022 for CubeCraft Bedrock.
Please do keep in mind that if you select large time periods the data might not load in because you try to load too much at once. I recommend using the time selection tool (little clock at the top right, could be hidden behind 3 dots on mobile) and select timespans not larger than a year.