This likely is not a bug in Obsidian as it is not hard-coded to use a specific browser. It is the configuration of the operating system that determines what application is used.
I’ve detected the cause, and use symlink as a workaround:
Condition
OS: Ubuntu 22.04
Obsidian: 1.5.12 SNAP installed via Ubuntu Software
Default browser: Chrome set default for current $USER
Link destination opened from Obsidian: Firefox
Detection
Install obsidian-open-link-with plugin to manually open link in Chrome.
A strange looking browser appear
=> It must use different profile from $USER!
I checked profiles used in these 2 browser instances with the following results.
chrome://version/: Profile Path:
Normal browser used by $USER: $HOME/.config/google-chrome/Default
Strange browser used by Obsidian: $HOME/snap/obsidian/current/.config/google-chrome/Default
Conclusion: The Obsidian app uses a separate home dir placed in side SNAP ($HOME/snap/obsidian/current/), so all settings like .config/ and .local/ are separated from the $USER’s settings at $HOME.
Solution (workaround)
Remove the Chrome config (.config/google-chrome/) inside SNAP, if anny, then create a symlink to the normal Chrome config of $USER:
Additional info about the time I opened Chrome from Obsidian:
A strange looking browser appear and ask to set Chrome as default again
=> Seems like Obsidian’s invoking a brand new user different from the current $USER!
=> It must use different profile from current $USER!