Why am I known as a user?

I inherited a Linux server; the previous administrator is no longer with our company. I can log in to the server via SSH with my company-wide Microsoft Directory administration user, and it works perfectly. I have sudo privileges. But I can't figure out why. This is my nsswitch.conf:

# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the glibc-doc-reference' and info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd:         compat ldap
group:          compat ldap
shadow:         compat ldap
gshadow:        files

hosts:          files dns
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

I would have expected to see myself with my user in the getent passwd command, but that's not the case:

myadminaccount@SERVER-NAME:~$ getent passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
_apt:x:100:65534::/nonexistent:/usr/sbin/nologin
systemd-timesync:x:101:101:systemd Time Synchronization,,,:/run/systemd:/usr/sbin/nologin
systemd-network:x:102:103:systemd Network Management,,,:/run/systemd:/usr/sbin/nologin
systemd-resolve:x:103:104:systemd Resolver,,,:/run/systemd:/usr/sbin/nologin
messagebus:x:104:110::/nonexistent:/usr/sbin/nologin
sshd:x:105:65534::/run/sshd:/usr/sbin/nologin
administrator:x:1000:1000:administrator,,,:/home/administrator:/bin/bash
systemd-coredump:x:999:999:systemd Core Dumper:/:/usr/sbin/nologin
_rpc:x:106:65534::/run/rpcbind:/usr/sbin/nologin
mik:x:998:1001:OMD site mik:/omd/sites/mik:/bin/bash
Debian-exim:x:107:114::/var/spool/exim4:/usr/sbin/nologin
myadminaccount@SERVER-NAME:~$

The user seems to be known but the group not:

myadminaccount@SERVER-NAME:~$ ls -l | head -n4
insgesamt 384
-rw-r--r-- 1 myadminaccount 5001 11854  6. Feb 2023  update_2022-02-06.log
-rw-r--r-- 1 myadminaccount 5001 46374  7. Nov 2022  update_2022-11-07.log
-rw-r--r-- 1 myadminaccount 5001  8192  6. Mär 2023  update_2023-03-06.log
myadminaccount@SERVER-NAME:~$ ls -ln | head -n4
insgesamt 384
-rw-r--r-- 1 2173 5001 11854  6. Feb 2023  update_2022-02-06.log
-rw-r--r-- 1 2173 5001 46374  7. Nov 2022  update_2022-11-07.log
-rw-r--r-- 1 2173 5001  8192  6. Mär 2023  update_2023-03-06.log

At a minimum, the hostname of the Active Directory server, a password or key for the connection, and the information that my user has sudo privileges should be configured somewhere on the server. But where? And why isn't my username listed in getent passwd? Where should I read and look to find out more? The server is SMP Debian 5.10.226-1 (2024-10-03) x86_64.