How can I get a log of the updates I installed recently?

The history of the commands apt, apt-get and the like is stored in the directory /var/log/apt in the file history.log:

pduck@host > cd /var/log/apt
pduck@host > ls -l history*
-rw-r--r-- 1 root root  3312 Dez  8 16:10 history.log
-rw-r--r-- 1 root root  3863 Mär  2  2018 history.log.10.gz
-rw-r--r-- 1 root root 28259 Feb  2  2018 history.log.11.gz
-rw-r--r-- 1 root root  3994 Nov 29 20:21 history.log.1.gz
-rw-r--r-- 1 root root  1618 Nov  2 19:06 history.log.2.gz
-rw-r--r-- 1 root root   421 Sep 22 14:03 history.log.3.gz
-rw-r--r-- 1 root root   908 Aug 31 16:06 history.log.4.gz
-rw-r--r-- 1 root root  1654 Jul 29 12:22 history.log.5.gz
-rw-r--r-- 1 root root  2298 Jun 30 18:34 history.log.6.gz
-rw-r--r-- 1 root root  2227 Jun  1  2018 history.log.7.gz
-rw-r--r-- 1 root root  2438 Apr 28  2018 history.log.8.gz
-rw-r--r-- 1 root root  4369 Mär 31  2018 history.log.9.gz

The file history.log is the current logfile. It gets rotated by the logrotate job in /etc/logrotate.d/apt once a month and kept for 12 months:

/var/log/apt/history.log {
  rotate 12
  monthly
  compress
  missingok
  notifempty
}

To view logs from previous months look into the *.N.gz files, e.g.:

zless /var/log/apt/history.log.1.gz

(No need to unzip them first, zless (and zgrep) does this under the hood.)

Another route is to examine /var/log/dpkg.log and its archives:

zgrep "2018-11.* status installed" /var/log/dpkg.log* | sort -t- -k2 -r

Notes:

• This command will also include packages that were already installed on your system but updated in the month of November 2018. Change 2018-11 to whatever other period you wish to examine.
• You can increase the number of archives saved on your system by following https://askubuntu.com/a/421072/248158.