fonts – IntelliJ: Cannot diasble ligatures for read-only files

How can I disable ligatures for all files (including read-only) in IntelliJ Idea Community edition 2020.3? The setting doesn’t work, even after restart:

The setting is turned off, but the "not equals" sign is still replaced

It works for non ready-only files. I tried restarting, but it doesn’t help. Is my only option to use a font that doesn’t support ligatures? If so, is there an easy was to install the “JetBrains Mono” font without ligatures?