rtkit is very spammy and floods syslog with messages. To disable this:

sudo mkdir /etc/systemd/system/rtkit-daemon.service.d
sudo vi /etc/systemd/system/rtkit-daemon.service.d/log.conf
[Service]
LogLevelMax=notice

sudo systemctl daemon-reload
sudo systemctl restart rtkit-daemon.service

example default log entries:

2025-09-25T16:50:01.621145+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:50:46.567089+01:00 gondor rtkit-daemon[3523893]: message repeated 2 times: [ Supervising 1 threads of 1 processes of 1 users.]
2025-09-25T16:51:16.834824+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:51:16.835098+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:52:03.967559+01:00 gondor rtkit-daemon[3523893]: Supervising 0 threads of 0 processes of 0 users.
2025-09-25T16:52:08.135322+01:00 gondor rtkit-daemon[3523893]: message repeated 3 times: [ Supervising 0 threads of 0 processes of 0 users.]
2025-09-25T16:52:08.138487+01:00 gondor rtkit-daemon[3523893]: Successfully made thread 3879793 of process 3879726 owned by '1000' RT at priority 10.
2025-09-25T16:52:08.138571+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:52:17.583393+01:00 gondor rtkit-daemon[3523893]: message repeated 2 times: [ Supervising 1 threads of 1 processes of 1 users.]
2025-09-25T16:52:47.811163+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:52:47.811432+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:53:48.485585+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:53:48.485747+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:54:10.318289+01:00 gondor rtkit-daemon[3523893]: Supervising 0 threads of 0 processes of 0 users.
2025-09-25T16:54:14.102492+01:00 gondor rtkit-daemon[3523893]: message repeated 3 times: [ Supervising 0 threads of 0 processes of 0 users.]
2025-09-25T16:54:14.106124+01:00 gondor rtkit-daemon[3523893]: Successfully made thread 3880384 of process 3880316 owned by '1000' RT at priority 10.
2025-09-25T16:54:14.106220+01:00 gondor rtkit-daemon[3523893]: Supervising 1 threads of 1 processes of 1 users.
2025-09-25T16:54:18.757125+01:00 gondor rtkit-daemon[3523893]: message repeated 2 times: [ Supervising 1 threads of 1 processes of 1 users.]