There is another workaround exists which can be used when an alias directive is used in conjunction with the try_files one (see this answer for an example). Can you try the following config?

server { listen 443 http2; listen [::]:443 http2; server_name api.com; root /srv/default/public/; # default root when no version location ~ ^/api/v1(?<v1route>/.*)? { alias /srv/api-v1/public; try_files $v1route /api/v1/index.php$is_args$args; location ~ ^/api/v1/index\.php$ { internal; include /etc/nginx/fastcgi.conf; fastcgi_param SCRIPT_FILENAME /srv/api-v1/public/index.php; fastcgi_read_timeout 300; fastcgi_pass unix:/run/php-fpm-php7.2.socket; } } location ~ ^/api/v2(?<v2route>/.*)? { alias /srv/api-v2/public; try_files $v2route /api/v2/index.php$is_args$args; location ~ ^/api/v2/index\.php$ { internal; include /etc/nginx/fastcgi.conf; fastcgi_param SCRIPT_FILENAME /srv/api-v2/public/index.php; fastcgi_read_timeout 300; fastcgi_pass unix:/run/php-fpm-php7.2.socket; } } } 

Temporary update (to be expanded with explanation)

OP asks an additional question:

There's one slight issue with the defaults Symfony expects. The following three server variables $_SERVER['DOCUMENT_URI'], $_SERVER['SCRIPT_NAME'] and $_SERVER['PHP_SELF'] equal /api/v1/index.php but default Symfony nginx generates /index.php, is there a way to tweak that in the above?

I don't think this is the reason of incorrect Symfony behavior. While this variables of course can be tweaked, the most probable reason is incorrect $_SERVER['REQUEST_URI'] value. With the configuration above it will be equal to /api/v1/some/path but most likely Symfony expects just /some/path instead. Here is the configuration you can try to overwrite that variable:

map $request_uri $api_ver { ~^/api/v([12])/? $1; } map $request_uri $api_route { ~^/api/v[12](/[^?]*)?(?:$|\?) $1; } server { listen 443 http2; listen [::]:443 http2; server_name api.com; root /srv/default/public; # default root when no version location ~ ^/api/v[12]/? { alias /srv/api-v$api_ver/public; try_files $api_route /api/v$api_ver/index.php$is_args$args; location ~ ^/api/v[12]/index\.php$ { internal; include /etc/nginx/fastcgi.conf; fastcgi_param REQUEST_URI $api_route$is_args$args; fastcgi_param SCRIPT_FILENAME /srv/api-v$api_ver/public/index.php; fastcgi_read_timeout 300; fastcgi_pass unix:/run/php-fpm-php7.2.socket; } } } 

I think this should fix your issues, but if you really want to tweak $_SERVER['DOCUMENT_URI'], $_SERVER['SCRIPT_NAME'] and $_SERVER['PHP_SELF'], you can add two additional lines to the nested location:

 location ~ ^/api/v[12]/index\.php$ { internal; include /etc/nginx/fastcgi.conf; fastcgi_param REQUEST_URI $api_route$is_args$args; fastcgi_param DOCUMENT_URI /index.php; fastcgi_param SCRIPT_NAME /index.php; fastcgi_param SCRIPT_FILENAME /srv/api-v$api_ver/public/index.php; fastcgi_read_timeout 300; fastcgi_pass unix:/run/php-fpm-php7.2.socket; } 

but I don't think it is required for correct Symfony behavior.

Update 2

To prevent $_SERVER['REQUEST_URI'] variable from being an empty string, you have the following options:

1. Redirect the request from /api/v1 or /api/v2 to /api/v1/ or /api/v2/ (seems the best as for me):

   map $request_uri $api_ver { ~^/api/v([12])/ $1; } map $request_uri $api_route { ~^/api/v[12](/[^?]*)(?:$|\?) $1; } server { ... location ~ ^/api/v[12]$ { return 301 https://$host$uri/$is_args$args; } location ~ ^/api/v[12]/ { alias /srv/api-v$api_ver/public; try_files $api_route /api/v$api_ver/index.php$is_args$args; location ~ ^/api/v[12]/index\.php$ { internal; include /etc/nginx/fastcgi.conf; fastcgi_param REQUEST_URI $api_route$is_args$args; fastcgi_param SCRIPT_FILENAME /srv/api-v$api_ver/public/index.php; fastcgi_read_timeout 300; fastcgi_pass unix:/run/php-fpm-php7.2.socket; } } } 

2. Explicitly add the trailing slash to the exact /api/v1 or /api/v2 requests:

   map $request_uri $api_ver { ~^/api/v([12])/? $1; } map $request_uri $api_route { ~^/api/v[12](?:/([^?]*))?(?:$|\?) /$1; } server { ... location ~ ^/api/v[12]/? { alias /srv/api-v$api_ver/public; try_files $api_route /api/v$api_ver/index.php$is_args$args; location ~ ^/api/v[12]/index\.php$ { internal; include /etc/nginx/fastcgi.conf; fastcgi_param REQUEST_URI $api_route$is_args$args; fastcgi_param SCRIPT_FILENAME /srv/api-v$api_ver/public/index.php; fastcgi_read_timeout 300; fastcgi_pass unix:/run/php-fpm-php7.2.socket; } } } 

If the $_SERVER['REQUEST_URI'] variable value should be prepended with /api string, you can try fastcgi_param REQUEST_URI /api$api_route$is_args$args; instead of fastcgi_param REQUEST_URI $api_route$is_args$args;.

If you want to tweak $_SERVER['DOCUMENT_URI'], $_SERVER['SCRIPT_NAME'] and $_SERVER['PHP_SELF'] variables, add the

fastcgi_param DOCUMENT_URI /index.php; fastcgi_param SCRIPT_NAME /index.php; 

lines to the nested location.