Unable to mount and erase Time Machine partition on external drive

Hello. I've had a 1TB Seagate Backup Plus Slim for more than a year now, and it's been partitioned 3/4 as an ExFAT drive and 1/4 as an APFS Time Machine drive. It's been working fine up until today.

Yesterday, I was able to perform a TM backup but stopped it at "Cleaning up (or something along those lines)..." Ejected and removed it after. When I plugged it into my MacBook Pro (2019, 13", 2 TB3, macOS 12.5) via a USB-C Hub today, the TM partition did not show up. Plugged it in directly to the TB3 port using the appropriate cable, and still nothing. Restarted the laptop and still nothing. Disk Utility shows my drive like this:

Trying to mount gives me this error:

So I tried running First Aid on it, and it still returns an error:

So seeing as the drive is "corrupted," I tried to reformat it using Disk Utility. Still, I got an error.

I also tried searching the error code 49218, and Apple Developer forums told me to input

sudo pkill -f fsck

in Terminal right after attempting to mount using Disk Utility. Now the error showed is com.apple.DiskManagement.disenter error 0. The post said it only worked for ExFAT drives, but I still tried it.

How can I reformat the drive? If I can't recover the contents, then I'm fine with reformatting. It's just that Disk Utility isn't letting me reformat. Any help would be appreciated. Thank you!