As shown in the screenshots, Time Machine had backed up 22.8 MB by 5:45 PM and only 23.8 MB over an hour later! An hour per MB?
I can hear the backup drive churning away.
The backup drive is less than half full and has over 4.6 TB left.
Mac mini, macOS 10.15
Time Machine is slower on large rotational drives that may be 5200 rpm and with small drive caches. Speed also depends on whether it is consolidating daily, weekly and monthly backups, the health of the drive, and the size of the files earmarked for backup. Yours appears unworldly slow though…
All of my currently in use Macs use a 2 TB Crucial X8 SSD (1050 MB/s) and most backups happen so quickly that I am unaware of their occurrence. I have a 3TB 7200 rpm drive with 64 MB cache backing up a 2011 Mac mini. Those backups go quite fast too.
You might consider booting into Recovery (cmd+R) and uses Disk Utility First Aid on your Time Machine drive in case there is something fixable through that process that is causing unusual slowness. May not make a difference.
If Time Machine is slow on Mac - Apple Support offers a few suggestions.
Why is Time Machine going so slow?
