Change repository, package mirror

Mirror information is located in /etc/installurl file. Unlike on Linux, where package managers usually offer extensive features like multiple repositories with different priority settings etc., on OpenBSD, there's just a single file with a single URL.

Open the /etc/installurl file in an editor and put a single URL from this mirror list into the file.

$ doas vi /etc/installurl

There's no need to update repositories like on Linux, it will automatically use the new repository when installing or updating packages, which you can try with pkg_add -u -v