unable to access

AS mentioned...

Mostly you just need a more modern Browser than Safari on Mojave, or High Sierra like Firefox or Brave.

https://brave.com/

https://www.mozilla.org/en-US/firefox/83.0/system-requirements/

Firefox 83.0 System Requirements (mozilla.org)

Opera…

https://www.opera.com/download/requirements

Opera system requirements | Opera

Thanks to dialabrain…

Firefox 112 is now the current version. runs in High Sierra.

https://www.mozilla.org/en-US/firefox/new/

If you are on High Sierra or earlier that is possible. The version of Safari in High Sierra is out-of-date.

For some reason some versions of Safari have difficulties with some web sites. Sometimes if Safari is updated (with the upgrade of the OS) the problem is solved, but not always. The only solution I know of is to do what you have done, have a second browser to use for the problematic web sites.

I hate to mention it but Firefox is now at 113.0.1. :)

I think Firefox has new releases more than any other browser. And for some reason, within a couple days they have a .1 release. Makes me wonder why they don't wait a couple days to include the change.

We have 7 Macs at home with Firefox as the default. Makes for a lot of updates. 😛

That doesn't even include Windows and Linux VMs.

:)