RStudio Server Preview: Font rendering in ACE editor broken (again)

Just upgraded a Ubuntu 16.04 VM with RStudio Server Preview v1.3.911 and the rendering of fixed-width font (anti-aliasing?) inside the ACE editor is broken. I attached a screenshot from Chrome on my Ubuntu 19.10 client.

Til now I had only noticed that problem in RStudio Desktop, but the latest Server Preview release is now also affected.

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I don't use Ubuntu so I'm not entirely sure if your issue is due to the same root cause as mine, however I did report an issue with macOS Catalina subpixel antialiasing on non-Retina displays here:

Selectively enable subpixel antialiasing on macOS Catalina

A toggle to enable/disable subpixel antialiasing at the application level (e.g., as is available in iTerm2) would appear to be an useful solution to both of our issues.

Indeed, I realize this is a tricky one, probably upstream bug in ACE editor and nothing to do with RStudio's implementation.

Monospace fonts (incl. "Ubuntu Mono") render nicely in Ubuntu / Chrome otherwise (pic below).

How can I locate older RStudio Preview releases to downgrade?

In addition, I can confirm that the offending CSS is related to inline ace_editor.css rules. Removing these rules fix the font rendering for me. I'm just not able to identify which exact rule or combination is the problem.

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Showing normal (Ubuntu Mono) font rendering below:

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Would you mind filing this as a bug report at https://github.com/rstudio/rstudio/issues?

Done! Thank you.