Suspension on my laptop (closing the lid) causes Wifi to not be available.

I'm not sure what the question here is. Are you wondering which level of suspension you want your laptop to go into when you close the lid?

You should understand ACPI sleep states when trying to setup whatever active states you want your machine to be in when you close the lid, because there is a chain of events that happen when you do so. Your machine may only support one, or a few states (s0-s3) that may not allow this. The first step is above, and the second is understanding what state your machine is being put into once you close that lid, so start there with Mint configuration and how it's dealing with the lid closing.

You need to unload your wifi module before suspend.

Without systemd it's easy:

create a file /etc/pm/config.d/config containing:

HOOK_BLACKLIST="wireless"
SUSPEND_MODULES=”NAME_OF_YOUR_WIFI_MODULE”
SUSPEND_MODULES=”wl”

With systemd try this

create a file /usr/lib/systemd/system-sleep/fix-wifi.sh containing (fuck this editor, replace the "##" with "&&") :

#!/bin/bash
[ "$1" = "post" ] ## exec /usr/sbin/modprobe NAME_OF_YOUR_WIFI_MODULE
[ "$1" = "pre" ] ## exec /usr/sbin/modprobe -r NAME_OF_YOUR_WIFI_MODULE
exit 0

and make it executable with chmod 755 /usr/lib/systemd/system-sleep/fix-wifi.sh

Is your laptop, by any chance, an HP? I had the same issue with wifi and finally, after about a year of frustration, found the solution HERE. To save a click, here's the part that worked for me, with the disclaimer that I don't honestly know how this works, but by the time I found it I was frustrated enough to run random code from the internet with sudo privileges on my main machine:

First, create the file

/etc/systemd/system/hp-keycodes.service

and type/copy-paste the following into it:

[Unit]
Description=HP setkeycodes fix

[Service]
Type=oneshot
Restart=no
RemainAfterExit=no
ExecStart=/usr/bin/setkeycodes e057 240 e058 240

[Install]
WantedBy=rescue.target
WantedBy=multi-user.target
WantedBy=graphical.target

Then, run the following commands:

sudo systemctl daemon-reload
sudo systemctl enable --now hp-keycodes.service

That fixed it for me, hopefully it helps you (or someone else) as well!

Looking at the Arch Wiki, it looks like this is a known issue. Give this solution a go:

https://wiki.archlinux.org/title/MSI_GS65#Wifi_is_hardblocked_(airplane_mode)_after_waking_up_from_suspend

EDIT: on closer look, it's not much of a solution. I assume you've tried restarting the network service and that doesn't work either? Possibly you could automate the airplane mode key twice by triggering that after waking from suspend....

Do you have Nvidia GPU? I am not sure if that could be related, but sometimes my old laptop would behave funky after resuming it from sleep when using nouveau driver. Although generally I just wouldn't get any video output. But I could never get past login screen, and it sounds unlikely it would affect WiFi, but who knows?

Any additional details you can add would go a long way towards troubleshooting. That desktop are you using (ex: Gnome, KDE, etc) and what model of laptop, the full hardware specs including CPU, GPU, WiFi model, etc. Finally, you'll want to look at the system logs to see if there's anything useful in there after resuming from sleep (journalctl).

It's been a while, but if I recall correctly Linux has always had issues with resuming from suspend. I would set it to not suspend, make closing the lid do nothing.