well as i have been having this issue and …
although it does appear to be resolved , your drivers/settings and monitor config can cause mayhem and upset it
not only does this issue affect UE5 editor it affects other apps
my experiances with the issue started with UE5
2 displays a dell 28" 4k (primary), and a sony 64" 4k tv (in original config desktop side by side extended)
using the nouveau drivers , my system respected the high dpi font settings , and did this automaticaly , and the fonts where all in sync , nothing too small nothing too big system wide ,
i now know that UE5 needs the official nvidia drivers not the nouveau ones , but it did get as far as starting the project selection menu (where yes the font sizes where tiny)
changing to the nvidia drivers is where the issues started for me
i swiched the primmary display to the sony tv , leaving the dell as a side screen for reading setup instructions as i went along , then found issues with other system apps
not supporting high dpi fonts , like google chrome not just ue5, ended up cnaging a lot of systems settings and app zooms manualy to get it about right , but still the super tiny font issues persisted
but by acident this morning i finaly found the solution it also seems to be the underlying cause of another issue i thought had been resolved by something else ,
mainly UE5 editor crashing on selecting an object , that i can now place as a nvidia driver monitor configuration issue
if the dell monitor is primary and the sony set to be a clone , no crash on UE5 and high dpi fonts are honerd system wide (no need for the ctrl+shift+w it works )
but if i set the sony monitor as primary back to supper small unreadable fonts and UE5 editor crashes on selecting object
far to say , other than i now have to manualy adjust back all the manual font changes i had to make (leaving most apps now having super large fonts) that the issue is not a UE5 issue , but a monitor config issue in the nvidea drivers !!!
as i tend to switch desktop configs arround on the fly depending on what im doing (given the sony tv is used sometimes for other than the pc ) it also explains why as if by magic the fonts all suddenly work , then later not type of random effect on newly started apps
hope this helps others with the same issue as its not always easy to have a different monitor on hand , but it dose point to it beeing down to the monitor profiles , given it may detect the sony and the modes correctly , but theres other stuff in the drivers list of monitor profiles , all i can say if your having this problem your monitor is not listed in them
sorry for the long post