I have a SAP Fiori installation behind an Nginx reverse proxy, no matter what I do with proxy_pass %2F in URL always gets decoded to /, I've tried a pletora of different configurations but the result is always the same.

location / {
# tried all of the following...
proxy_pass https://x.x.x.x:xxxx;
proxy_pass https://x.x.x.x:xxxx/;
proxy_pass https://x.x.x.x:xxxx$uri;
proxy_pass https://x.x.x.x:xxxx$request_uri;
proxy_pass https://x.x.x.x:xxxx/$uri;
proxy_pass https://x.x.x.x:xxxx/$request_uri;
# additional config below, not much, the vhost configuration is pretty straight forward
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Scheme $scheme;
}

Any idea?

EDIT: Worth to mention I guess, Nginx version is 1.18.0 running on Debian 11.