Is Tom's Simple CSS plugin still being maintained?

I've seen Simple CSS mentioned in this forum a few times as a good way to add custom CMS to GeneratePress projects. I like the way you can add CSS to individual pages and the dark theme :)

However Wordpress tells me it has not been updated in over a year and through 3 major revisions of Wordpress and may therefore no longer work reliably.

Just wondering if it is something I still can/should use? Is it still recommended as a good way to add custom CSS to GeneratePress/Blocks projects or is there a new way now?

I don't really like adding CSS through the customiser's narrow left column...

I'm using a child theme so I could add CSS in style.css there but I'm not sure if/how I can access that through the WP admin or if I have to work on the file locally and keep uploading it by FTP which is doable but a bit of a pain...