WP-admin giving 404

Since you rename the original plugin folder and create a blank plugin then it works. If in case log file is not immediately reflecting the error or it is not obvious for identifying the error. Moving the disabled plugin one by one to the new empty plugin folder is another way to find out which plugin(s) cause the issue.

One or more of the plugins generate php error which I believe.
I suggest you turn on the debug with output file to trace.
You may do the following steps to debug.

1. Update your wp-config.php by adding the following statement

// turn on debug mode
define( 'WP_DEBUG', true );

// the path to file, WP_DEBUG must be TRUE to use
define( 'WP_DEBUG_LOG', 'path_to_log/debug.log' );

2. rename back the plugin folder

3. run the site once

4. go to see the debug.log to find out the error portion

If you haven’t done anything, most likely, your host update PHP version I guess.
There are many factors, just see the debug log to find out.

For more about debug, you may visit Debug WordPress