DragonFlyBSD

On a fresh install of 6.4, when attempting to install a package, the following message is received:

root@server0:/tmp # pkg update                                                                   
Updating Avalon repository catalogue...
Certificate verification failed for /C=US/O=Let's Encrypt/CN=R3
Certificate verification failed for /C=US/O=Let's Encrypt/CN=R3
Certificate verification failed for /C=US/O=Let's Encrypt/CN=R3
34395427332:error:14FFF086:SSL routines:(UNKNOWN)SSL_internal:certificate verify failed:/usr/src/lib/libressl/../../crypto/libressl/ssl/tls13_client.c:609:
pkg: https://mirror-master.dragonflybsd.org/dports/dragonfly:6.6:x86:64/LATEST/packagesite.txz: Authentication error
Unable to update repository Avalon
Error updating repositories!

Editing /usr/local/etc/pkg/repos/df-latest.conf and changing 'https' to 'http' results in a working update.

Also, an attempt to fetch a file:

root@server0:/tmp # fetch https://download.freebsd.org/releases/amd64/amd64/ISO-IMAGES/13.1/FreeBSD-13.1-RELEASE-amd64-memstick.img.xz
Certificate verification failed for /C=US/O=Let's Encrypt/CN=R3
Certificate verification failed for /C=US/O=Let's Encrypt/CN=R3
Certificate verification failed for /C=US/O=Let's Encrypt/CN=R3
34380796420:error:14FFF086:SSL routines:(UNKNOWN)SSL_internal:certificate verify failed:/usr/src/lib/libressl/../../crypto/libressl/ssl/tls13_client.c:609:
fetch: https://download.freebsd.org/releases/amd64/amd64/ISO-IMAGES/13.1/FreeBSD-13.1-RELEASE-amd64-memstick.img.xz: Authentication error

Just for good measure, downloaded source and rebuilt world/kernel and rebooted, but whatever is causing the problem remains.

Interestingly, a few other machines with recent 6.4 installs do not exhibit this issue.

Suggestions?