I can confirm dmesg on Ubuntu 21.10 gives me "Operation not permitted", even though my user is in the "adm" group:
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 21.10
Release: 21.10
Codename: impish
$ ls -l /var/log/dmesg*
-rw-r----- 1 root adm 100336 Mar 13 17:01 /var/log/dmesg
-rw-r----- 1 root adm 94365 Mar 13 16:40 /var/log/dmesg.0
-rw-r----- 1 root adm 23990 Mar 13 15:00 /var/log/dmesg.1.gz
-rw-r----- 1 root adm 23017 Mar 9 21:50 /var/log/dmesg.2.gz
-rw-r----- 1 root adm 23295 Mar 4 18:51 /var/log/dmesg.3.gz
-rw-r----- 1 root adm 23253 Feb 24 21:34 /var/log/dmesg.4.gz
$ id
uid=1000(marji) gid=1000(marji) groups=1000(marji),4(adm),5(tty),10(uucp),20(dialout),24(cdrom),27(sudo),30(dip),46(plugdev),121(lpadmin),132(lxd),133(sambashare),134(docker)
$ dmesg
dmesg: read kernel buffer failed: Operation not permitted
I can confirm dmesg on Ubuntu 21.10 gives me "Operation not permitted", even though my user is in the "adm" group:
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 21.10
Release: 21.10
Codename: impish
$ ls -l /var/log/dmesg*
-rw-r----- 1 root adm 100336 Mar 13 17:01 /var/log/dmesg
-rw-r----- 1 root adm 94365 Mar 13 16:40 /var/log/dmesg.0
-rw-r----- 1 root adm 23990 Mar 13 15:00 /var/log/dmesg.1.gz
-rw-r----- 1 root adm 23017 Mar 9 21:50 /var/log/dmesg.2.gz
-rw-r----- 1 root adm 23295 Mar 4 18:51 /var/log/dmesg.3.gz
-rw-r----- 1 root adm 23253 Feb 24 21:34 /var/log/dmesg.4.gz
$ id 1000(marji) ,4(adm) ,5(tty) ,10(uucp) ,20(dialout) ,24(cdrom) ,27(sudo) ,30(dip) ,46(plugdev) ,121(lpadmin) ,132(lxd) ,133(sambashare ),134(docker)
uid=1000(marji) gid=1000(marji) groups=
$ dmesg
dmesg: read kernel buffer failed: Operation not permitted