Thank you for the detailed answer @Nalates Urriah. I have tried dropping the bandwidth to 1500, 1000 and 500 to no avail. My modem is brand new as I moved into this apartment and got the new ISP (and new high end fiber modem) less than a month ago. @Lyssa GreymoonStreaming services and YouTube pause no problem, no buffering or any issue of the sort. Restarting it didn't change anything either.
I looked at the secondlife.log file and I see things that might be part of the issue but have no idea if I'm right and how to fix it if I am. I don't know how to attach it here so I uploaded it to my Google Drive if it can be any use to figure out my issue.
I know it doesn't come from SL since until late July before I moved everything was working fine and since then the only thing that changed was my internet connection. maybe I need to open a port in the modem or something of the sort but I'm not sure how to do that and don't want to screw up everything else while trying to fix one thing.
Also, yes I tried varied regions, both empty and busy ones and nothing changes, within 5-6 minutes UDP drops to 0 and I get disconnected.