Launching the Slack interface pops up the following notification on the bottom right corner:

(You're accessing Slack with a third-party
app that is out-of-date.)
Updating the Chrome backend?
A notification appears.
Rambox: v0.6.3
OS: Manjaro Illyria 18.0.2, Linux Kernel 4.20.7
Arch: x64
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same problem here v0.6.3 on Ubuntu 18.10
from https://get.slack.help/hc/en-us/articles/115002037526
"Starting on March 15, 2019, we are changing the minimum browser requirements needed to run Slack. Please make sure your browser is up to date."
This issue it's gonna be addressed in the upcoming new version
@fvulich When is that gonna be? Any ETA?
When will new version comes?
Now I even get this:

@vaisov Did you update to 0.6.4?
Works on 0.6.4. Thanks!
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Most helpful comment
This issue it's gonna be addressed in the upcoming new version