I ran into an issue where my custom dynamic dns settings were partially overwritten. By partial I mean the service record that resides within /etc/config/ddns was still there, but the corresponding line within /usr/lib/ddns/services (actually, what looks to be the entire file) was overwritten with the update. I get that direct modifications to certain files is probably not something that is protected when an update occurs, but the comments in those config files do say they can be edited to add additional ddns providers/services so it's a little misleading if they are going to be overwritten.
On the plus side I have a device (smart scale) on the 2.4GHz band that had been having pretty consistent connectivity issues and those seem to be much better after the update. Not entirely sure what changed that could be helping but hey, I'll take the win for now.