Post the text of the error message, please. If it’s the message I think it is, the message is warning that you may not be connecting to the intended website; to the website that you want to connect to.
Which means either you’re connecting to a fraudulent website intercepting your traffic, or that the particular site you’re connecting to is presenting itself inconsistently. Inconsistent connection data during the secure connection can be from a fraudulent site intercepting your traffic. Or can be from a misconfigured website.
Put differently, you’re being warned the site you have connected to may not be the website you wanted to connect to.
If the site you connecting to is not fraudulent, then the website maintainers will need to reconfigure their DNS domain and/or the host name and/or the connection security certificates that they are using. They’ll need to look a little less like a fraudulent site; less like a host that is intercepting web traffic.
Inform the website maintainers that they’ve set up their web server security incorrectly, and suggest they look into it.
If by “big tech interference”, you mean some folks who have misconfigured their web server connection security (what probably happened), or that you’re potentially connecting to a website that you didn’t intend to (actual fraudulent connection), yes.
While unlikely, it’s also possible that some few websites might deliberately misconfigure their own website security settings, to intentionally provide the appearance of a conspiracy against them. The particular motivation for a misconfiguration being far more difficult to assess remotely, of course. But this case seems unlikely.
Avoid fraud by using encrypted websites in Safari on Mac - Apple Support
A previous reply here references Google Safe Browsing, which is a different matter.