I know this question has been asked and answered for previous versions of Ubuntu, but in my searches I have not seen anything directly related to v. 18.10. I am running Ubuntu 18.10 on a System 76 Lemur laptop, with an Intel® Core™ i3-7100U CPU @ 2.40GHz × 4 and an Intel® HD Graphics 620 (Kaby Lake GT2) processor.
At screen resolutions of 1920x1080 and 1680x1050, the system-wide fonts are so small as to be almost unreadable.
One suggested solution has been to adjust the scale in Settings/Displays, but in Ubuntu 18.10 this only toggles between 100 and 200%, neither one of which is satisfactory.
Another proposed solution has been to go to Settings/Universal Access and choose the text size; again, in 18.10 I can only choose between normal or Large text, and I have already set it to Large. This helps the system fonts, such as in the Settings dialogs, but does not help header fonts on applications like Firefox or Thunderbird.
I'd appreciate some more up to date advice on what to do.