If you're on a recent macOS + iPad, there's Universal Control[0] (I use this as a way to have chat/mail on a second monitor). If you don't mind some noticeable latency, you can use it as a second display via Sidecar[1]. Finally, you can do the same thing described in the article with any terminal emulator app and SSHing into the remote system (I've had luck with Prompt[2], which is available as a one-time $15 purchase).
From the Readme, their eventual plan for the project is to be able to serve the client through the web browser which would mean that almost all tablets would be supported.
If you're referring to the outdated certificates, I installed Let's Encrypt's ISRG Root X1 Certificate onto my old iPad 4 and that seems to have taken care of it. Local sites served over HTTP never had any issues.
[0]: https://support.apple.com/en-us/HT212757
[1]: https://support.apple.com/en-us/HT210380
[2]: https://panic.com/prompt/