Could this be considered PBN?

I have 5 websites on the same server. Each domain has been registered for 4-5 years and has several dozen or several hundred subpages / blog entries. Of course, 1 domain is the most important.

If every website brings something new to the user and is not a typical PBN, can Google consider it a PBN? I would like to add links to the main subpage of the main website on the other 4 websites.

Should I do it or skip it? It's the casino niche, where getting backlinks is extremely difficult.

If you interlink it and leave footprints yes it’ll be considered as pbns

It depends on the quality of your properties. I would not take any risk and remove footprints even if it's looks like a legit site.

You can read here about footprints:
https://www.cultblogger.com/pbn-footprints/

Thanks for help!

IG Professor said:

It depends on the quality of your properties. I would not take any risk and remove footprints even if it's looks like a legit site.

You can read here about footprints:

Click to expand...

Great source!

So basically, the best thing to do, would be backlink-swap with other webmasters with no reciprocal links?

Just like this:
(X - other, external websites), (A - my main domain), (B - my other domains)

(B) -> (X) and (X) -> (A) ?