📚 Web-Based Linux Server Emulators?

Hello r/Linux!

I am looking for any good web-based Linux server emulators to be able to practice linux command line on public PCs such as public library or school PCs. Do any of you know of any good ones?

Thanks so much for any help with this!

Edit: Ideally it would be a free service, though I know this may be hard to find or may not exist. Basically, a way to get practice with Linux server command line without having to download anything as that's usually not allowed on public library or school PCs.