You can set things like :-

# mount /tmp as a tmpfs.  Defaults to no; set to yes to enable (/tmp
# will be part of the root filesystem if disabled).  /tmp may also be
# configured to be a separate mount in /etc/fstab.
RAMTMP=yes

Geoff

the discard option that was stopping my tmpfs folders from being mounted

Yeah, RAM doesn't support TRIM.

Don't apply options that you don't understand.

From mount(8):

So you should only use that option for SSDs that support TRIM (confirm with lsblk --discard).

Also note that /dev/shm and /run are already mounted with tmpfs by default.

You should stick to a single problem per thread.

FWIW automounting of USB sticks is handled by GVFS & udisks2 via thunar (the file manager), it has nothing to do with the init system.

mount: wrong fs type, bad option, bad superblock on ramdisk[...], 
missing codepage or helper program, or other error

In some cases useful info is found in syslog - try dmesg | tail or so

I tried dmesg | tail and found out that it was the discard option that was stopping my tmpfs folders from being mounted so I removed them, tried mount -a again and then got this message.

mount: /run: filesystem mounted, but mount(8) failed: No such file or directory
mount: mount point /var/lock is a symbolic link to nowhere
mount: /run: filesystem mounted, but mount(8) failed: No such file or directory
mount: /dev/shm: filesystem mounted, but mount(8) failed: No such file or directory
mount: /dev/johndoe/Downloads: filesystem mounted, but mount(8) failed: No such file or directory

However, I tested each and every one of my tmpfs folders by adding an empty file into them and rebooting. They were gone from all of them once I rebooted so it looks like my ramdisk is fully working.

However, during this ordeal, I came across a couple of problems.

Whenever I tried to open /etc/fstab with nano (even with sudo) on the terminal, it opens the file but it shows up blank with a message reading Error reading lock file /etc/.fstab.spwp: Not enough data read.

Also, when inserting USB sticks used to mount them automatically, they are unmounted and clicking them in the file explorer brings up a password prompt to eject them and my user password doesn't work. It happened. I think, after I fixed the tmpfs.

My only guess is that it could be caused by OpenRC (the init software I am using), being in the experimental phase.
I also installed Devuan without any non-free or contrib software

Here is my setup in /etc/fstab

ramdisktmp /tmp tmpfs rw,discard,noatime,nosuid,noexec,nodev,mode=1777,size=2G 0 0
ramdiskrun /run tmpfs rw,discard,noatime,nosuid,noexec,nodev,mode=1777,size=2G 0 0
ramdiskvarlock /var/lock tmpfs rw,discard,noatime,nosuid,noexec,nodev,mode=1777,size=2G 0 0
ramdiskvarrun /var/run tmpfs rw,discard,noatime,nosuid,noexec,nodev,mode=1777,size=2G 0 0
ramdisktmp /dev/shm tmpfs rw,discard,noatime,nosuid,noexec,nodev,mode=1777,size=2G 0 0
ramdiskhome /home/johndoe/Downloads tmpfs rw,discard,noatime,nosuid,noexec,nodev,mode=1777,size=8G 0 0

I was hoping to move these directories above into tmpfs ramdisks, including my Home's downloads folder.
I tested it out by putting an empty text file in the downloads folder then reboot the VM.
But upon booting up, I found the file was still there when it should've been wiped out with the RAM.
That same Downloads folder, as I defined in the fstab file, was also visible as a mountable disk, like an external drive, on the desktop although I wasn't able to without root access.

To elaborate, although I can still access the Downloads folder in the file explorer, I can't mount it from the desktop. Whenever I do, I get the following error message.

Mount Failed
mount: only root can mount ramdiskhome on /home/johndoe/Downloads

Any help would be much appreciated.
Thanks.