Go to a command line and enter:
fdisk /dev/sdX
or
fdisk /dev/nvmeX
You will get:
Disk /dev/nvme0n1: 476.96 GiB, 512110190592 bytes, 1000215216 sectors
Disk model: Samsung SSD 970 PRO 512GB
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000
Device Boot Start End Sectors Size Id Type
/dev/nvme0n1p1 2048 1000215215 1000213168 477G 83 Linux
The boot start should be 2048 for 1MiB alignment. If it is 64, the alignment is 4k.
SSDs formatted in 6.8 will be compatible with 6.9, but not the other way around.