It's been an ongoing and somewhat contentious issue for a while now.

Just want to remind that the certificate issue is still active.

Firefox does not show http version the http://aurora2.pentarch.org/ => server not found
Firefox shows the site via https with the manual security exception

Chrome does not give a chance to make a security exception and does not show the https site
Chrome follow the HSTS redirection from http to https and again give no chance to make a security exception.

It is not possible to use chrome for aurora2.pentarch.org for me, for now.

3 other browsers allow me to make security exceptions. So the site is accessible after all, but strangers needs to have strong intention to use it.

If I saw a security warning for the webpage of an old looking game I’d assume the domain was taken over by scammers and back out.

Scammers are not paying the hosting fees

All that said, for new people coming along, they're likely to just see the page get blocked by their browser, and not knowing any better are likely to not come back.

This is the main thing to me - I'm not saying Aurora needs to have a full-blown PR recruitment campaign, but it's better if we are reducing barriers to entry for people to keep the forum community robust and healthy. Some folks will never even think to use something as ancient as a "forum" in this modern era of Discord and Reddit, and that's fine, but for the folks who will use a forum I think it's best not to make that any trickier than it has to be, where possible and reasonable to do so.

There also is a cost involved with having a public certificate.

No there isn't.  Industry pays the internet security research group with the understanding that it will amongst other things provide LetsEncrypt certs for no charge.  All you need to do is reissue it every year, which is true of every cert.