The permissions on /media with the ACL are the default and do work normally in linux distros and so are not likely to be the issue. There should be no need to alter them, other than experimental purposes.
The fact that access to the usb was available manually means that there's no fundamental issue with the mounting process.
The other variables that exist at first glance are:
the virtualisation aspect of ubuntu;
the nautilus file manager;
automatic mounting.
To check whether the automatic mounting is actually working, after inserting the usb, run the command:
findmnt in a terminal and inspect the output. In the following example output snippet shown, the usb partition:
/dev/sda1 has been mounted on /mnt, rather than /media, but in your case it should be on /media/... , but this is what it looks like:
Code:
$ findmnt
<snip>
│ └─/run/credentials/[email protected] tmpfs tmpfs ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap
├─/tmp tmpfs tmpfs rw,nosuid,nodev,nr_inodes=1048576,inode64
├─/boot/efi /dev/nvme0n1p1 vfat rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro
└─/mnt /dev/sda1 vfat rw,relatime,fmask=0000,dmask=0000,allow_utime=0022,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-
If the usb happens to be mounted, but nautilus cannot locate it, the problem appears to be with nautilus.
If the usb partition has not been automatically mounted, then you can configure that in gnome. There are a few ways to do it, one of which is using the Disks utility, select the usb, find the mount options and select the one that will mount the usb at start up. I can't give more specific details not having used gnome for some time.
If nautilus appears to be the problem you could try other filemanagers to see whether they behave properly. Other filemanagers include: Thunar, Nemo, PCManFM. There are many others.
In relation to the virtualsation aspect being implicated in this problem, I can't say not having used the sort of virtualisation you have described, so that's one for further research if no other resolution appears.
In relation to ACLs, there's a manual page: man acl, which provides a terse introduction to the matter. There are similarly man pages for getfacl and setfacl. There may be more explanatory expositions online.
In relation to the mounting of a usb, it is only partitions that are mounted, not the raw disk device, so what would actually be mounted is /dev/sdb1 or /dev/sdb2, and not /dev/sdb since /dev/sdb represents the disk device, not a partition. To be able to read a filesystem, one needs to access the partition which holds it.
In relation to presenting of data for readers, as you have wisely done, it's best done using code tags so the exact output is shown in its original format and not distorted and corrupted as the output is in post #3 where the emoji has been introduced. There's info on code tags here:
https://www.bbcode.org/how-to-use-bbcode-a-complete-guide.php. Alternatively, in the reply top panel, under the the three vertical dots, is the </> icon which can also be used to place text in code tags.
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