I am already rewriting several different legacy URLs that existed in the /forums/ subdirectory, please point out any existing links which don't work yet, and I'll get them implemented as well. Rather than using explicit URL rewriting, I instead chose to use 301 redirects to the new location.

    location @old_forums {
        if ($args ~* "/?showforum=[0-9]+") {
            return 301 $scheme://$host/index.php/board,$arg_showforum.0.html;
        }
        if ($args ~* "/?act=SF&s=(|.+?)&f=[0-9]+") {
            return 301 $scheme://$host/index.php/board,$arg_f.0.html;
        }
        if ($args ~* "/?showtopic=[0-9]+&view=findpost&p=[0-9]+") {
            return 301 $scheme://$host/index.php/topic,$arg_showtopic.msg$arg_p.html#msg$arg_p;
        }
        if ($args ~* "/?showtopic=[0-9]+") {
            return 301 $scheme://$host/index.php/topic,$arg_showtopic.0.html;
        }
        if ($args ~* "/?showuser=[0-9]+") {
            return 301 "$scheme://$host/index.php?action=profile;u=$arg_showuser";
        }
        return 301 $scheme://$host/;
    }

    location /forums/ {
        try_files $uri @old_forums;
    }

    location ~ /forums/index.php$ {
        try_files $uri @old_forums;
    }

    location @old_forums {
        if ($arg_showforum ~ ^[0-9]+$) {
            return 301 $scheme://$host/index.php/board,$arg_showforum.0.html;
        }
        if ($arg_act = "SF") {
            set $test_sf A;
        }
        if ($arg_f ~ ^[0-9]+$) {
            set $test_sf "${test_Sf}B";
        }
        if ($test_sf = AB) {
            return 301 $scheme://$host/index.php/board,$arg_f.0.html;
        }
        if ($arg_showtopic ~ ^[0-9]+$) {
            set $test_showtopic A;
        }
        if ($arg_view = "findpost") {
            set $test_showtopic "${test_showtopic}B";
        }
        if ($arg_p ~ ^[0-9]+$) {
            set $test_showtopic "${test_showtopic}C";
        }
        if ($test_showtopic = ABC) {
            return 301 $scheme://$host/index.php/topic,$arg_showtopic.msg$arg_p.html#msg$arg_p;
        }
        if ($test_showtopic = A) {
            return 301 $scheme://$host/index.php/topic,$arg_showtopic.0.html;
        }
        if ($arg_showuser ~ ^[0-9]+$) {
            return 301 "$scheme://$host/index.php?action=profile;u=$arg_showuser";
        }
        return 301 $scheme://$host/;
    }

    location /forums/ {
        try_files $uri @old_forums;
    }

    location ~ /forums/index.php$ {
        try_files $uri @old_forums;
    }

Could not log in under my account,  cleared cache etc.
No lost password emails being received. Any way forum could set up temp email account like hydrogen audio at Gmail so members who can't log in can contact admin?

Still a few superficial elements that I'd change. But clearly what pleases one will annoy another. The only suggestion I'll remake is regarding the use of shadows on text. To me it's unnecessary and looks naff - it just looks cleaner without IMO. See pic.

2 - I'm not a fan of user ranks ("Hero Member"?) based on post count.  Gamifying quantity over quality tends to encourage some undesirables.

@dhromed
In the forum’s thread list threads with unread posts have a “New” button that links to the first unread post (see attachment).

From top to bottom: original, soft shadow 0.5 opacity, 0.3 opacity, no shadow.

4. On small screens, the format of the 'Recent topics' on the front page isn't easy to read - not sure why it is formatted differently from the topic lists in individual forums.

Hmmm, Coreda's look a little bolder - but anyway -- big improvement! Thanks kode54, clearly a lot of hard work - looking really good.

Will the new board support Tapatalk ?