According Cisco:
Deauth reason 2 means that the previous authentication is no longer valid.
Meaning that you likely had changed between wpa2 and wpa3 this means the device hangs on a encryption key which no longer is recognized.
^ of course it is possible to sent a deauth with any code, but i see this as a very low chance, i see this always happen on my network after a upgrade some devices just work very broken in these scenarios even when i restart them, so its worth to identify them.
See it like ssl certificates for a bit as example, when this has been changed the certificate fail, likely due to the change, the router sents a different wpa2 key than before even though password remains unchanged, so it is advised to forget wifi and re-associate keys.
As for snort...
snort is very resource intensive you need atleast 4gb ram, while the flint 2 uses 7-8gb ram, it also shares it as storage, and a minimum requirement of a dual core, flint 2 uses quad so you are fine... but snort takes a while to correctly configure + i don't believe this version comes with ui.
^ then snort also constantly reads and writes, this is not so recommended on flash memory.
My advise if you really like a IDS system to have it appart from your router 
on the other hand you can also look into something lighter like banip, this is less evasive but blocks malicious ip.