On a recent list from March (and also February - below) that used various defensive metrics, The Athletic had him fourth.
Here's a quote from Nico Hischier saying Matthews should be considered.
Here is one from The Hockey Writers, which you also referenced:
In this article, we look at why Auston Matthews deserves consideration for the Hart Trophy in the 2023-24 season.
thehockeywriters.com
Another from The Toronto Star, which you will probably say is biased, but I would argue still more credible than 'Sportskeeda' and 'Clutchpoints':
Matthews is celebrated for his goal scoring but this NHL season has seen the Maple Leafs star mature into a complete 200-foot player.
www.thestar.com
While this is based on Tavares thinking Matthews should be considered, it's still another example of it being mentioned on another site, which you said wasn't the case:
Leafs centre Auston Matthews is seven goals away from 70 with seven games left in the regular season. Matthews is aiming to become the NHL's first 70-goal scorer since Teemu Selanne and Alexander Mogilny each scored 76 during the 1992-93 season. Mark Masters has more on his chase for the milestone.
www.tsn.ca
I don't think Matthews is going to win the Selke or anything, but you said he wasn't mentioned anywhere on the internet and then I found a bunch of examples in a minute or two, including some very relevant ones like The Athletic.