Timshift wont let me select proper snapshot location (wrongly concludes no space)

[ghost]

Describe the bug
did a fresh install of mx linux and before i could use timeshift but not now. Is doesnt accept my luks partition an a backup location anymore and i do not know why. It has over 200 Gb of free space. First time worked like a charm but not anymore. Does anyone know what i am missing?

I tried:
sudo timeshift --snapshot-device /dev/mapper/root.fsm (or /dev/sda3)

but it still says it has to little space

$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 238.5G 0 disk
├─sda1 8:1 0 256M 0 part /boot/efi
├─sda2 8:2 0 512M 0 part /boot
├─sda3 8:3 0 229.7G 0 part
│ └─root.fsm 253:0 0 229.7G 0 crypt /
└─sda4 8:4 0 8G 0 part
└─swap 253:1 0 8G 0 crypt [SWAP]
sr0 11:0 1 1024M 0 rom

$ df -H
df: /run/user/1000/doc: Operation not permitted
Filesystem Size Used Avail Use% Mounted on
udev 8.4G 0 8.4G 0% /dev
tmpfs 1.7G 1.5M 1.7G 1% /run
/dev/mapper/root.fsm 242G 9.0G 221G 4% /
tmpfs 5.3M 4.1k 5.3M 1% /run/lock
tmpfs 3.4G 67M 3.3G 3% /dev/shm
/dev/sda2 511M 275M 200M 58% /boot
/dev/sda1 265M 281k 265M 1% /boot/efi
cgroup 13k 0 13k 0% /sys/fs/cgroup
tmpfs 1.7G 0 1.7G 0% /run/user/118
tmpfs 1.7G 17k 1.7G 1% /run/user/1000

$ sudo timeshift --check --verbose

Select backup device:

Num Device Size Type Label
0 > /dev/sda4 8.6 GB luks
1 > /dev/sda2 510.9 MB ext4 boot
2 > /dev/sda3 246.7 GB luks

Enter device name or number (a=Abort): 2

E: Failed to mount device '/dev/disk/by-uuid/' at mount point '/run/timeshift/backup'
E: mount: /run/timeshift/backup: /dev/disk/by-uuid is not a block device.

E: Not enough disk space (< 8.0 GB)
E: Select another device or free up some space

E: Not enough disk space (< 8.0 GB)
E: Select another device or free up some space

To Reproduce
Steps to reproduce the behavior:

1. Install MX linux
2. Install Timeshift
3. Select RSYNC
4. Try to select the proper snapshot location

Expected behavior
To be able to select my main partition

Screenshots

System:

• Linux MX 21 KDE
• Timeshift 21.09.1-1

[jasmineyang-jk]

I met the same issue on Debian system. Expecting someone sharing more info on how to fix this issue.