Funnily I was thinking of you as they announcing, threatening, imposing a new lockdown... In a few more hours, I'm heading to the beach. I live two km away, with family, sandwiches quite happy to get sunshine once again like last week! Good luck with your new "normalcy"
Anyway I'd like to know how that affects network shares. Let's assume l installed an untouched Windows 7 SP1 pro zero updates.
Aside that SMB is a continuously moving target, because security additions, different defaults and so on (so the lack of updates can affect surely the access on newer OSes), you didn't have a SMB problem you had a DNS problem and is hard to say what problem it was, given all the test we did, and w/o having access to your logs and your machine.
Let me guess, one of your machine OS is HOME EDITION ? That's a well known problem when HOME machines are mixed with Pro/Ent.... We would have fixed that in 20 seconds if you mentioned that.
W7 Professional and W10 21H2 Education Well known? I didn't know the existence of such issue. I'm not seeing that problem announced when I launch my chrome browser with google home page or in a Walmart's sales newspaper...
So that's strange, but clearly for somewhat reason one of the OS started to behave like a Home one, switching to the so called by Microsoft "simplified networking". Everything is relative, nowadays the average "apple like" user uses a thumb-drive or a cloud drive, or even a remoting sw, rather than learn how the LAN works. But in the early days of XP sharing a file between a professional and a home PC required a degree (in MS stupidity) + some voodoo rituals + a pilgrimage to Santiago de Compostela + something I forgot