Comment 3 for bug 1936175

Something similar was done for checking for the latest Ubuntu release and updating the MOTD in LP:1836475. It switches the download part into a systemd timer (https://launchpadlibrarian.net/505544658/lp1836475-focal.debdiff). So maybe something similar here where the timer job checks existence and timestamp of a file and runs if it doesn't exist or is older than a certain period of time.

Then the apt hook itself would remove that file forcing the systemd timer job to fire.