I'd say finding a virus on Linux will be hard (to my knowledge, there are no Linux viruses in the wild). Rootkits are a different thing: booting from a clean medium (e.g. a live CD), and running chkrootkit would come to mind.
chkrootkit is a well-known rootkit detector (I've used it in the past, many years ago – hadn't a reason to use it afterwards, luckily)...
This might be what you are looking for:
Jitsi is a set of open-source projects that allows you to build and deploy secure videoconferencing solutions.
The source code is here.
You can use the browser as the client (multiplatform), and there is an SDK for Android and iOS.
The are no fixed limits (your resources will define that). No privacy information. ...
I found this one quite handy. It is a ruby gem, that allows CLI viewing of Markdown files.
if you are using Ubuntu:
sudo apt install ruby
sudo gem install mdless