So maybe we temporarily fixed the issue with Friendica, tho is too early so be sure.
I have deleted and re-added the mariadb.cnf file like the yunohost team suggested.

Then in etc/php/7.3/fpm/pool.d/friendica.conf I made sure I still have these:

pm = static
pm.max_children = 500
pm.max_requests = 1000

#Execute and serve PHP files
    location ~* \.php$ {
    fastcgi_connect_timeout 300s;
    fastcgi_send_timeout 300s;
    fastcgi_read_timeout 300s;  
        fastcgi_split_path_info ^(.+?\.php)(/.*)$;
        try_files $uri =404;
        fastcgi_pass unix:/var/run/php/php7.3-fpm-friendica.sock;
        fastcgi_index index.php;    
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }

So far it works. But let's see.... #ŧromlive