You can get an output, almost similar to the linux command “last” using a script.
cat << "EOF" > /root/last
#!/bin/sh
logread -e dropbear | grep 'Password auth succeeded for' | sed 's/^.* dropbear\[//' | sed 's/\]:.*//' | sort -u > /tmp/procids
successfullogins="/tmp/procids"
while IFS= read -r procid
do
user=$(logread -e "$procid" | grep 'Password auth succeeded for' | sed 's/^.*succeeded for //' | sed 's/ from.*//')
ip=$(logread -e "$procid" | grep 'Password auth succeeded for' | sed 's/^.*from //' | sed 's/\:.*//')
starttime=$(logread -e "$procid" | grep 'Password auth succeeded for' | sed 's/authpriv.*//' | sed 's/ from.*//')
endtime=$(logread -e "$procid" | grep 'Exited normally' | sed 's/authpriv.*//' | sed 's/ from.*//')
if [ -z "$endtime" ]; then
endtime="still logged in"
fi
echo -e "$user\t$ip\t$starttime"- "$endtime"
done < "$successfullogins"
exit 0
EOF
chmod 755 /root/last
root@OpenWrt:~# /root/last
'root' 192.168.2.135 Mon Jun 7 14:44:58 2021 - Mon Jun 7 15:21:42 2021
'root' 192.168.2.135 Mon Jun 7 15:21:13 2021 - Mon Jun 7 15:21:16 2021
'root' 192.168.2.135 Mon Jun 7 15:22:02 2021 - Mon Jun 7 17:05:10 2021
'root' 192.168.2.135 Mon Jun 7 16:31:55 2021 - Mon Jun 7 17:04:41 2021
'root' 192.168.2.135 Mon Jun 7 17:08:24 2021 - Mon Jun 7 17:33:35 2021
'root' 192.168.2.135 Mon Jun 7 17:15:01 2021 - Mon Jun 7 17:33:25 2021
'root' 192.168.2.135 Mon Jun 7 17:33:50 2021 - still logged in
Tested with 19.07.7