A concept: in Linux, there are only read-only files, read-only directories, and no read-only users.

To achieve this, you must change the entire system files and directories to read-only, which is very bad and dangerous:

chmod -R 0744 /

At the same time, modify the permissions of the directory (directory:/home/user 1) of the logged-in user (for example: user1) to:

chmod -R 0444 /home/user 1

In this case, the user 1 will only have read-only access to the system, but logging in the user will face a lot of warnings/error prompts.