Frontend design and content of secondary sites in multisite

Every subsite is a complete WordPress site.

And every WordPress site requires its own theme.

This can be a completely separate theme, or the same theme that’s activated individually for each subsite.

When you activate the same theme for multiple subsites, changes made in Customizer (for classic themes) or Site Editor (for block themes) are stored in the database separately for each site, so there’s no problem with changes made in one site overriding another site. Of course, if you edit the theme’s files directly those edits will affect all subsites using the theme.

So think of this (from a design/theme perspective) as working on separate, independent WordPress sites! And if this analogy doesn’t fit what you’re trying to achieve, then multisite may not be the best choice for you ??

Thanks George for responding, but that I know. Perhaps I can explain as follows. Each site has its own domain name with own URL.
So is this the way?:
Design the entire site (permalinks, blocks, content) in the primary site.
How are the secondary sites designed? Copy the primary structures to each secondary? Or redesign each secondary site?
One would think that since the same DB etc is shared there should be some quick way to replicate the primary design into the secondaries, but I find nothing on the web about this.

How are the secondary sites designed?

Assume you have different WordPress sites even with different hosting providers. How will you design/build each of these different sites?

That’s exactly what you’d do here.

One would think that since the same DB etc is shared there should be some quick way to replicate the primary design into the secondaries,

You claimed you “know” what I said earlier, yet your “thinking” betrays that claim. That may be your expectation, but that’s not how WordPress multisite works.

Again, WordPress subsites are complete WordPress sites by themselves. They share the same infrastructure (file system and database), but each subsite has its theme and plugins activated separately.

When you activate a theme or plugin on one subsite, it’s only activated on the subsite. Even when you network-activate a theme or plugin, they’re still independently configured and don’t share any settings or data. Users are also not shared by default: when someone registers on one subsite, they’re only registered on that particular subsite — they can’t automatically login to any other subsite!

There are many hosting providers out there that use WordPress multisite to offer “managed WordPress” instances to their customers. Each customer’s site is obviously very different, runs its own theme and set of plugins, has its own users, etc. This is a perfect use-case for multisite.

Yeah, that’s how I understand it. Perhaps: the “back-end” is the same, the front-ends not. But the same data can be served on the different sites as the DB is shared. The question is about sharing tables with other sites – to what extent can content be shared?
Thanks!

Each subsite has its own set of database tables, even though they all share the same database. See:

https://codex.www.ads-software.com/Database_Description#Multisite_Table_Overview

But the same data can be served on the different sites as the DB is shared.

This is not a built-in feature. You’ll have to find a plugin to do this, or write custom code if no plugin exists. This is all I’ve been trying to say all along ??

The question is about sharing tables with other sites – to what extent can content be shared?

The upper limit is whatever you’re capable of coding. That’s because even where WordPress does not provide any native functions, you can always make direct database queries to do pretty much whatever you want.