As usual, Debian and Ubuntu packages were made available as part of the release process: https://www.syslog-ng.com/community/b/blog/posts/installing-the-latest-syslog-ng-on-ubuntu-and-other-deb-distributions

openSUSE / SLES and Fedora / RHEL unofficial repositories are maintained by me, and now updated to 4.8.1: https://www.syslog-ng.com/community/b/blog/posts/installing-latest-syslog-ng-on-rhel-and-other-rpm-distributionsIf you use the syslog-ng48 repo, then you do not have to change anything, just start an update.

my syslog-ng-stable repos for RPM distros will be updated next week, as I always wait a few days.

updates for FreeBSD ports are now submitted, but might take some time. If you urgently want to test 4.8.1, then you can use ports files from my GitHub repo: https://www.syslog-ng.com/community/b/blog/posts/installing-a-syslog-ng-4-development-snapshot-on-freebsd