I have seen this exact issue with uBlock Origin Lite on Chrome 137.0.7151.41 (latest). I have also seen similar performance issues if you manually block the js files under https://www.torn.com/js/debug/. I don't know if this is a Sendbird thing or not, but there are definitely issues with page load that go away if you whitelist *.torn.com on uBlock.
EDIT
Thought I'd add a bit more detail of the debugging I did in case it is useful. Opening the JS console, I saw a couple of CSP and ERR_BLOCKED_BY_CLIENT error messages related to air.torn.com (which also seems related to some telemetry scripts in the js/debug/ folder?) I tried blocking requests to this domain with Chrome's "network request blocking" feature, but these seemed to make the issue worse. Whitelisting *.torn.com in uBlock instead made page loads responsive again, but opening the console I now see the calls to air.torn.com are failing with a "Failed to load resource: the server responded with a status of 503 ()" error but this does not seem to affect page speed on Chrome Desktop at least
This feels like a nice option. Maybe, in universe, you could justify it as an expert trying to specifically chase "elusive" or "thrilling" targets that they haven't gotten to yet.
I think the biggest killer enjoyment-wise for me was building up 90+ targets and not caring about any of them since they didn't help with the uniques I had...