Many of us find our eyes have a difficult time changing focus as we get older. As a result, we find the teeny-tiny type sizes employed by many web sites and applications difficult to read. Typography is a big subject for another day, although I'll say that I like the defaults applied by Bootstrap.
One way to deal with the readability problem (which you often notice only after confusing commas and periods a few times) is to increase font scaling from 100% to 125% or more. The clear downside to this on 1K or lower resolution displays is that you lose screen real estate. But it does work. At least it did for me.
Ubuntu Desktop 18.04 only gives you the option of doubling (to 200%) font scaling in Settings... Devices. That's insane. Fortunately, the Gnome Tweak Tool (a/k/a "Tweaks") allows you to raise scaling by whatever fractional amount you want (although the actual result may vary depending on your display card and monitor).
To change font scaling in the Gnome Tweak Tool, go to "Fonts" and then change the number in the "Scaling Factor" window. By default this is set to 1.00. In my case changing it to 1.25 worked well. I have read that some people find even 1.10 to be a noticable improvement.
Ubuntu now supports fractional scaling in 25% increments from 100 - 225% with version 22.04, which doesn't entirely obsolete this article but probably makes it less likely you'll need to separately mess with font scaling.