If you recently upgraded the Slack Desktop App on Debian and now are wondering what happened to your automatic HiDPI recognition: Don't worry any further. It's a little peculiar, since this regression doesn't seem to be well documented on the net. However, the solution is easy. Slack on the Desktop is an Electron app - therefore it generally supports the same flags that other Electon Apps (like Spotify) support and Electron has a flag since 2014
--force-device-scale-factor. On my Macbook Pro, I'm using a scale-factor of 1.5.
Here's a little convenience wrapper around the
slack binary to always start Slack with this setting. The same can be done for other Electron apps, as well.
#!/bin/sh /usr/bin/slack --force-device-scale-factor=1.5