I witnessed this absolute corker of a bug in the office today.

After a force reboot (its a long story), we noticed that the cursor was flickering on my colleague's Ubuntu laptop. After some googling, we realised that this flickering only happens at 200% fractional scaling. Setting to any other value like 175%, 150% etc. works perfectly fine.

https://askubuntu.com/questions/1234189/cursor-flickers-on-primary-display-when-fractional-scaling-is-enable-for-dual-mo

Despite the link above being more than three and a half years old, it appears that even today, this bug can still be observed in the wild, in its natural habitat, on Ubuntu.