The Ubuntu archive servers are currently under high load. To mitigate further performance problems, we enabled rate limiting of select Ubuntu packages, particularly the linux-firmware package. This enables us to serve all Ubuntu servers with updates, but the download time might be longer than normal.
We expect the high-load situation to remain until early next week and will gradually remove rate limiting.
If you want a quick remedy for your system, you can set up your Ubuntu system to download packages from one of the hundreds of community mirrors. This can be done permanently (see Option “A”) or as a one-off (see Option “B”) as explained in this Discourse article.