I got my Omega2+ last week and am still learning some basics.
One issue I got is this:

Card is plugged in but not visible after reboot

 root@Omega-ECFB:~# df
 Filesystem           1K-blocks      Used Available Use% Mounted on
 /dev/root                 5632      5632         0 100% /rom
 tmpfs                    62872       696     62176   1% /tmp
 /dev/mtdblock6           25664      2876     22788  11% /overlay
 overlayfs:/overlay       25664      2876     22788  11% /
 tmpfs                      512         0       512   0% /dev

Remove the card, plug back in:

 root@Omega-ECFB:~# df
 Filesystem           1K-blocks      Used Available Use% Mounted on
 /dev/root                 5632      5632         0 100% /rom
 tmpfs                    62872       696     62176   1% /tmp
 /dev/mtdblock6           25664      2876     22788  11% /overlay
 overlayfs:/overlay       25664      2876     22788  11% /
 tmpfs                      512         0       512   0% /dev
 /dev/mmcblk0p1         1863088      5664   1744736   0% /tmp/run/mountd/mmcblk0p1

Basically I'll always have the card there, so it'd be OK if I can just turn off the "mountd" thing and use fstab? or udev (already remembered that OpenWRT isn't exactly a udev thing)
I suppose anything I do there will be lost on a firmware update?

Not sure how this works.
Does anyone know how to always "see" the SD card on a poweron or boot?
I've formatted it as plain ext4.

And I've also read this:
https://community.onion.io/topic/1282/omega2-reboot-and-sd-card-fixed/30

But I think that was about general reboot issues and not mounting the card at all.

Both works and I'm on the right fw version I think:

root@Omega-ECFB:~# oupgrade -l
> Device Firmware Version: 0.1.10 b160
> Checking latest version online...
> Repo Firmware Version: 0.1.10 b163
> Comparing version numbers
> New build of current firmware available, upgrade is optional, rerun with '-force' option to upgrade

From what I understood b163 is a no-go for the 2+ and it'll also just not install it if I try. Please correct me if I got that one wrong.