Using tcpdump I can see there's no header for authentication :
20:52:41.631368 eth-met In IP nextcloud.http > rvprx.44736: Flags [P.], seq 1:1692, ack 889, win 503, options [nop,nop,TS val 2526802502 ecr 2849238942], length 1691: HTTP: HTTP/1.1 401 Unauthorized
E...<.@.@...
2.
2...P..v...H.......35.....
...F....HTTP/1.1 401 Unauthorized
Date: Mon, 20 Nov 2023 19:52:41 GMT
Server: Apache/2.4.57 (Debian)
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate
Pragma: no-cache
Content-Security-Policy: default-src 'none';
WWW-Authenticate: Basic realm="Nextcloud", charset="UTF-8"
Set-Cookie: oc_sessionPassphrase=xxxxxxxxxxxx%2xxxxxxxxxxxx%xxxxxxxxxxxxx%2Bvjbxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: __Host-nc_sameSiteCookielax=true; path=/; httponly;secure; expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=lax
Set-Cookie: __Host-nc_sameSiteCookiestrict=true; path=/; httponly;secure; expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=strict
Set-Cookie: xxxxxxxxxxxxxxkc=xxxxxxxxxxxxxxxxxxxxxxxxx; path=/; secure; HttpOnly; SameSite=Lax
Referrer-Policy: no-referrer
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-Permitted-Cross-Domain-Policies: none
X-Robots-Tag: noindex, nofollow
X-XSS-Protection: 1; mode=block
Connection: close
Content-Type: application/xml; charset=utf-8
<?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
<s:exception>Sabre\DAV\Exception\NotAuthenticated</s:exception>
<s:message>No public access to this resource., No 'Authorization: Basic' header found. Either the client didn't send one, or the server is misconfigured, No 'Authorization: Bearer' header found. Either the client didn't send one, or the server is mis-configured, No 'Authorization: Basic' header found. Either the client didn't send one, or the server is misconfigured</s:message>
</d:error>