macOS panic log header contains invalid panic log offset

I think your iMac has a hardware issue most likely with the Logic Board. The EtreCheck report shows your iMac has had about 20 "ProxiedDevice-Bridge" panics which are associated with the T2 security chip. Plus the most recent Kernel Panic log you posted actually mentions "Possible memory corruption" and the first Kernel Panic log you posted mentioned part of it was malformed which also suggests a memory issue.

I have personally found that the Logic Boards on the 2020 iMacs have a much higher rate of failure than any other iMac model I've seen while supporting Macs with my organization.

You can try running the Apple Diagnostics to see if any hardware issues are detected, however, most times the diagnostics will find nothing even when there is a confirmed hardware issue, but if it does indicate a problem at least you will know for certain.

For a future note, there is no reason to be using CleanMyMac or Avast. In fact Avast has been caught twice selling people's personal information. There is really no reason to be using MalwareByte's real time scanner either.

Effective defenses against malware and other threats - Apple Community

To confirm it is not a software issue you can perform a clean install or remove problematic files. These files should not be installed on a Mac:

• Cleaner
• Optimizer
• AnitVirus
• VPN

Remove:

• Cudo Miner
• Express VPN
• Avast
• CleanMyMac

Use any provided installer. You may get lucky and find it was just a software conflict. The mdworker process is working overtime trying to index your HD. If you are mirroring your LaCie drive using the Seagate Control Panel, you may want to try and unplug it and startup with just your internet drive to see if the Kernel Panic goes away. You may also be able to exclude the LaCie drive from Spotlight indexing.

Post several Kernel Panic logs in their entirety so we can examine them for clues and any patterns. You can find the Kernel Panic logs in "/Library/Logs/DiagnosticReports" with file names beginning with "kernel" or ending in ".panic". If there are no Kernel Panic logs in that folder, then check the "Retired" sub folder. Post the entire Kernel Panic logs here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar.

Also you can run the third party app EtreCheck and post the complete report here so we can examine it for clues. Plus this report will give us the exact model of your Mac which is very important.