How to uninstall macOS Big Sur Beta from a separate APFS volume?

I don't have a full answer for you. I think at least some of the problems you are having are related to this item in the Big Sur release notes:

• If macOS Big Sur 11 beta is installed into the same APFS container as previous versions of macOS, system software updates can no longer be installed on the previous versions of macOS. (64411484)

It seems that Big Sur is using an APFS volume format that is not recognized by Catalina.

I would tread very carefully here, starting with good backups of your Catalina volume. Then, you might try booting into the recovery partition and seeing if it recognizes the Big Sur volumes properly. If it does you could try deleting them from there.

Please understand, I have not tried this myself — it's just an idea.

What did you end up doing? I'm facing the same problem with the greyed out disk1s7 and an Update partition as well.

Hi, I had the same problem, didn't have enough time to actually test Big Sur, so what I did was:

• Boot from a Catalina usb installer

• Open disk utility

• Delete the Big Sur Data and Update containers

• Restart the machine and voíla, no more Big Sur, Catalina files and system untouched.

I hope it works for you.

• X.

I had a similar case. I installed Big Sur, I went through the problem of continuous reboot (see other thread), I decided to recover form a back-up I had of Catalina before Big Sur.
I ended up with a disk1s1 (empty), Macintosh HD data , another Macintosh HD data (not erasable with Home directory)and the Macintosh data with the OS.
What I did is to unmount the two volumes not in use.
For the moment I will wait to install next release of BigSur .
If you have a back-up prior to the installation of BigSur, the best solution is to erase the disk and recover from the back-up

Yep, i had same issue. Not only that, VirtualBox, Note, PDF, lots of apps are crashing.
Dam. Big Sur....

This worked for me

setapp.com/how-to/downgrade-from-big-sur-to-catalina

This was my setup: Catalina was first partition; created APFS second partition to test public beta versions of Big Sur

To remove the second partition I followed the following youtube video guidance without any bootable USB macOS version:
"How to Remove Partition on macOS | How to Delete a Partition on macOS" from Howza

The only thing I had to change was to select on the left (after erasure) the partitions I want to remove with the partition plus and minus sign on the top left, rather than going through the Right Click procedure, mentioned in the video. I assume that was due to my Catalina version.

A disk1s7 volume did appear in the process (also not shown in the video) and also appeared greyed out - however I first removed the 2nd (and now erased) partition first and then could select the greyed out disk1s7 entry and remove it with the partition minus sign as well.

All looking good and working well (knock knock knock)