Installed Arduino IDE version 1.8.10 64bit on Ubuntu 19.10. The software seems to be working fine but digits, spaces and tabs do not display when writing/pasting/opening code in the editor, which makes it completely unusable.
(I can delete tabs/spaces/digits and they display correctly when copy-pasting to a text file, so it's probably just a display problem).
Same issue with the console below as you can see in this screenshot: