'lvconvert --thin'  will now convert complete a pool + virt conversion 

 # RHEL9.3
 
kernel-5.14.0-362.8.1.el9_3    BUILT: Tue Oct  3 02:39:10 PM CEST 2023
lvm2-2.03.21-3.el9    BUILT: Thu Jul 13 08:50:26 PM CEST 2023
lvm2-libs-2.03.21-3.el9    BUILT: Thu Jul 13 08:50:26 PM CEST 2023
 
 
2. Conversion to thin pool (w/o specified meta volume):
[root@virt-494 ~]# lvcreate --yes  -n POOL1 -L 100M snapper_thinp
  Logical volume "POOL1" created.
[root@virt-494 ~]# lvcreate --yes  -n POOL2 -L 100M snapper_thinp
  Logical volume "POOL2" created.
[root@virt-494 ~]# lvcreate --yes  -n POOL3 -L 100M snapper_thinp
  Logical volume "POOL3" created.
[root@virt-494 ~]# lvconvert --thinpool snapper_thinp/POOL1
  Thin pool volume with chunk size 64.00 KiB can address at most <15.88 TiB of data.
  WARNING: Converting snapper_thinp/POOL1 to thin pool's data volume with metadata wiping.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
Do you really want to convert snapper_thinp/POOL1? [y/n]: y
  Converted snapper_thinp/POOL1 to thin pool.
[root@virt-494 ~]# lvconvert -T snapper_thinp/POOL2
  No command with matching syntax recognised.  Run 'lvconvert --help' for more information.
  Nearest similar command has syntax:
  lvconvert -T|--thin --thinpool LV LV
  Convert LV to a thin LV, using the original LV as an external origin.
 
[root@virt-494 ~]# lvconvert --thin snapper_thinp/POOL3
  No command with matching syntax recognised.  Run 'lvconvert --help' for more information.
  Nearest similar command has syntax:
  lvconvert -T|--thin --thinpool LV LV
  Convert LV to a thin LV, using the original LV as an external origin.
 
 
 
# RHEL9.4
 
kernel-5.14.0-362.8.1.el9_3    BUILT: Tue Oct  3 02:39:10 PM CEST 2023
lvm2-2.03.23-1.el9    BUILT: Tue Nov 28 02:15:42 PM CET 2023
lvm2-libs-2.03.23-1.el9    BUILT: Tue Nov 28 02:15:42 PM CET 2023
 
2. Conversion to thin pool (w/o specified meta volume):
[root@virt-247 ~]# lvcreate --yes  -n POOL1 -L 100M snapper_thinp
  Logical volume "POOL1" created.
[root@virt-247 ~]# lvcreate --yes  -n POOL2 -L 100M snapper_thinp
  Logical volume "POOL2" created.
[root@virt-247 ~]# lvcreate --yes  -n POOL3 -L 100M snapper_thinp
  Logical volume "POOL3" created.
[root@virt-247 ~]# lvconvert --thinpool snapper_thinp/POOL1
  Thin pool volume with chunk size 64.00 KiB can address at most <15.88 TiB of data.
  WARNING: Converting snapper_thinp/POOL1 to thin pool's data volume with metadata wiping.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
Do you really want to convert snapper_thinp/POOL1? [y/n]: y
  Converted snapper_thinp/POOL1 to thin pool.
[root@virt-247 ~]# lvconvert -T snapper_thinp/POOL2
  Thin pool volume with chunk size 64.00 KiB can address at most <15.88 TiB of data.
  WARNING: Converting snapper_thinp/POOL2 to fully provisioned thin volume.
Do you really want to convert snapper_thinp/POOL2? [y/n]: y
  Converted snapper_thinp/POOL2 to thin volume.
[root@virt-247 ~]# lvconvert --thin snapper_thinp/POOL3
  Thin pool volume with chunk size 64.00 KiB can address at most <15.88 TiB of data.
  WARNING: Converting snapper_thinp/POOL3 to fully provisioned thin volume.
Do you really want to convert snapper_thinp/POOL3? [y/n]: y
  Converted snapper_thinp/POOL3 to thin volume.
[root@virt-247 ~]# lvs -a -o +devices
  LV                   VG            Attr       LSize   Pool         Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices              
  POOL1                snapper_thinp twi-a-tz-- 100.00m                     0.00   10.84                            POOL1_tdata(0)       
  [POOL1_tdata]        snapper_thinp Twi-ao---- 100.00m                                                             /dev/sda(0)          
  [POOL1_tmeta]        snapper_thinp ewi-ao----   4.00m                                                             /dev/sda(75)         
  POOL2                snapper_thinp Vwi-a-tz-- 100.00m POOL2_tpool0        100.00                                                       
  POOL2_tpool0         snapper_thinp twi-aotz-- 100.00m                     100.00 11.62                            POOL2_tpool0_tdata(0)
  [POOL2_tpool0_tdata] snapper_thinp Twi-ao---- 100.00m                                                             /dev/sda(25)         
  [POOL2_tpool0_tmeta] snapper_thinp ewi-ao----   4.00m                                                             /dev/sda(77)         
  POOL3                snapper_thinp Vwi-a-tz-- 100.00m POOL3_tpool0        100.00                                                       
  POOL3_tpool0         snapper_thinp twi-aotz-- 100.00m                     100.00 11.62                            POOL3_tpool0_tdata(0)
  [POOL3_tpool0_tdata] snapper_thinp Twi-ao---- 100.00m                                                             /dev/sda(50)         
  [POOL3_tpool0_tmeta] snapper_thinp ewi-ao----   4.00m                                                             /dev/sda(78)         
  [lvol0_pmspare]      snapper_thinp ewi-------   4.00m                                                             /dev/sda(76)