I had the same problem. I use Appimage Obsidian 0.10.6 in mxlinux 19.2 using debian 10 buster as a base.
While I used the Googlechrome browser, I started the obsidian (appImage) and changed the themes, then it suddenly slowed down to a halt and no response. I see this could be a problem of the electron base or whatever. Then I closed it from the panel icon, and then restarted it, it seems ok.
Could this be due to themes? what if I had choosed the troublesome theme, then how do I reset it back to the default? Is this theme changing or other than default theme caused problem while changing? I don’t know.
I plan to install it thru snap package instead of appImage, then it asked me to install in user mode or system mode? I am planning to install as a system snap application, so it may have access all over them system.
Now it seems ok. I am not going to change the theme 80_neon which is selected by me. If the problem comes, I will raise it.