The answer provided by Boon is correct. I wanted to leave comment under that answer but apparently I need 50 points to comment so I can only add new answer…
After digging into the matter it sounds like the kde-open5 from kde-cli-tools is doing some funky lower-casing on first element of URL (slack://A/B/C becomes slack://a/B/C). This sounds like an old bug: https://bugs.kde.org/show_bug.cgi?id=429408
I suspect that slack changed in how they handle the links/links has changed – it aligns with slack upgrade in my case: slack-desktop:amd64 from 4.22.0 to 4.23.0.
Looking at process list:
- the slack website asks browser to open link with upper case
- kde-open5 is run with correct link
- slack is run with lower-cased workspace
I’ve reported this to slack with all the details so I hope it will be fixed.
Workaround:
Just adding some details to what (Boon suggested)
- Run the quick script in bash:
while sleep .1; do ps aux | grep slack | grep -v grep | grep magic; done
-
Try logging in to slack – accept login attempt in browser
-
You should see login link in console:
kde-open5 slack://WORKSPACE_ID/magic-login/...
/usr/lib/slack/slack --enable-crashpad slack://workspace_id/magic-login/...
- Open the slack with correct link:
/usr/lib/slack/slack --enable-crashpad slack://WORKSPACE_ID/magic-login/...